Construction & DIY Calculators

Work out the concrete for slabs, round slabs, footings, walls, columns, tubes, steps and curbs: cubic yards or m³ with waste, 40/50/60/80 lb premix bags, ready-mix order, weight and cost.

Calculate the concrete for footings from length, width, depth and count — in cubic yards and bags.

Calculate square footage for rectangles, L-shaped rooms, circles, triangles, trapezoids, borders and rings, with square yards, square meters, acres, waste and total cost.

Work out how many boxes of flooring you need from the room size, the coverage per box and a waste allowance.

Find how many tiles and boxes you need for a floor or wall from the area, tile size, grout joint, layout pattern and waste, with cost, grout and thinset estimates.

Estimate the gallons of paint for a whole room’s walls from the total wall length, height, coats and openings.

Estimate drywall sheets for walls and ceilings from the total area or the room size (minus doors and windows), with waste, plus screws, joint compound, tape, corner bead, board weight and the material and installed cost.

Roof area, squares and shingle bundles from the footprint and pitch (x/12, degrees or percent) for gable, hip and shed roofs, with waste, underlayment, ice and water shield, ridge cap, starter, drip edge, nails, tear-off and an installed cost estimate.

Convert roof rise and run into a pitch ratio, the slope angle in degrees and the area multiplier.

Gravel for a driveway, path or base: cubic yards, tons and bags for rectangles, circles, triangles, rings or a list of areas, with stone-type densities, compaction allowance, bulk vs bag cost and truckloads.

Find the cubic yards of mulch and the number of 2-cubic-foot bags for a garden bed by length, width and depth.

Calculate cubic yards and tons of topsoil for a lawn or bed from length, width and depth.

Estimate posts, rails and pickets for a fence from the total length and post spacing.

Find how many deck boards and how much linear footage you need from the deck size, board width and gap.

Work out the number of steps, the exact riser height, the tread run and the total run from your total rise.

Calculate board feet of lumber from thickness, width, length and quantity — and the total cost per board foot.

Estimate how many bricks a wall needs from its size or area, less doors and windows, for modular, standard, queen, king, Norman, Roman, utility, UK or Australian bricks or a custom size, any mortar joint, single or double wythe and header bonds, plus mortar volume, masonry cement or premixed bags, sand, courses and cost.

Find how many pavers you need for a rectangular or round patio, walkway or driveway from the paver size, joint width, laying pattern and waste — plus the gravel base, bedding sand, polymeric joint sand, edge restraint, excavation, pallets and total cost.

Estimate how many bags of batt insulation you need for an area, and the thickness a target R-value takes.

Calculate how many sheets of plywood or OSB you need for a floor, walls, a roof or any area — with waste, sheet sizes from 2 × 4 to 4 × 10 ft or custom, a whole-sheet layout count, nails, weight and cost.

Estimate the studs for a wall from its length, the on-center spacing, openings and corners.

Convert length, width and depth into cubic yards and cubic feet for concrete, gravel, soil or mulch.

Estimate the tons of hot-mix asphalt for a driveway or lot from length, width, thickness and mix density.

Work out how much tile grout to buy in pounds or kilograms and whole bags from the area, tile size and shape, tile thickness, joint width and grout type, with a coverage chart for every joint width and the cost.

Find how many deck boards you need from the deck size, board width, board length and a waste allowance.

Estimate concrete blocks and mortar bags for a wall from its length, height and block size.

Calculate cubic yards of topsoil or fill for a bed or lawn from length, width and depth.

Estimate the heating BTUs a room needs — by the quick climate rule of thumb (area, climate, ceiling height, insulation, sun) or a heat-loss estimate from the indoor and outdoor temperatures, walls, windows, ceiling, floor and air leakage — in BTU/h, kW, watts of electric heat and furnace input.

Size a solar array from your daily energy use, peak sun hours, panel wattage and system losses.

Find the right water heater size: the tank size and first-hour rating for an electric, gas or heat pump water heater from your household size or your peak-hour hot water use (DOE worksheet), or the flow rate, temperature rise and Btu/h or kW for a tankless unit.

Size an off-grid battery bank from your daily energy use, days of autonomy, system voltage and depth of discharge.

Size a ductless mini-split from room area, ceiling height, sun exposure, insulation, climate, occupants and kitchen load.

Find how many tiles to buy with a waste allowance for straight, diagonal or herringbone layouts: area, preset or custom tile size, grout joint, tiles per box, boxes to buy, leftover tiles and total cost.

Turn a building footprint and roof pitch into the true sloped roof area in square feet and roofing squares.

Estimate the rebar for a slab grid — number of bars, total linear feet and weight — from the slab size and bar spacing.

Calculate the bank and loose (hauled) volume of a dig in cubic yards, plus the number of truckloads, from length, width, depth and swell.

Estimate the segmental blocks for a retaining wall from the wall length, height and block size: courses, blocks per course, cap blocks, buried course, base and drainage gravel, drain pipe, filter fabric, geogrid, cap adhesive, block weight and material cost.

Estimate gutter length, downspouts, elbows and hangers for a house from the total eave length and downspout spacing.

Work out the linear feet of baseboard trim a room needs from its size and door openings, plus how many 8-ft or 16-ft pieces to buy.

Find the linear feet of crown molding to buy for a room from its perimeter and a waste allowance, plus the number of 8-ft pieces.

Sand for a paver base, sandbox or fill: cubic yards, tons and bags for rectangles, circles, triangles, rings or a list of areas, with sand-type densities, extra for compaction, bulk vs bag cost and truckloads.

Find how much sod a lawn needs for rectangles, circles, triangles or several areas: square feet with waste, rolls, slabs or mini rolls, full pallets plus loose pieces, cost by the square foot, piece or pallet, weight and topsoil.

Size an ADA wheelchair ramp from the rise and slope ratio — ramp run, landings and total length.

Estimate joint compound, pails or bags, paper or mesh tape and corner bead for a drywall job — from the number of sheets, the board area or the room size — for ready-mixed, lightweight or setting-type mud at finish levels 2 to 5, with the cost.

Calculate the concrete to set fence or deck posts — total cubic feet plus 60-lb and 80-lb bag counts — from the post and hole sizes.

Turn a wall and ceiling area into the number of drywall sheets, plus the screws, joint tape and compound to finish it.

Find the insulation thickness needed to reach a target R-value or the ENERGY STAR / IECC level for your climate zone, top up existing attic insulation, compare materials and check what a cavity depth delivers, in R and RSI.

Measure a room and get the linear feet of baseboard or trim you need, doorways subtracted, plus how many stock lengths to buy.

Count the deck boards for a rectangular deck from its size, board width and gap — with linear feet and the number of rows.

Count the pickets, posts and rails for a wood fence from its length, picket width, gap and post spacing.

Rebar weight in pounds, kilograms and tons for US bar sizes #2–#18, Canadian 10M–55M, metric 6–40 mm or any diameter: from bar count and length, a total length, or turn a weight back into bars, with laps, unit weights, bars per ton and cost.

Count the segmental retaining-wall blocks and cap blocks for a wall from its length, height and block size, with a buried course, waste, base gravel, drainage stone, drain pipe, geogrid estimate, pallets and material cost.

Estimate the tons of hot-mix asphalt for a driveway from its length, width and thickness, plus the material cost.

Balance a grading job: cut and fill volumes from zone areas and average depths or from a grid of cut/fill depths (borrow-pit method), with soil swell and compaction shrinkage, bank, loose and compacted volumes, the soil to haul off or import, truckloads, haul cost and the grade change that balances the site.

Lay out a staircase from a total rise: number of steps, exact riser height, total run and stringer length, with a comfort check.

Count the wallpaper rolls for a room from its size, ceiling height, roll dimensions and pattern repeat.

Grout for a whole tiling job: up to three areas (floor, walls, backsplash or mosaic) each with its own tile size, thickness and joint width, giving pounds or kilograms, bags, cost, joint length for sealing and a comparison of grout use across common tile sizes.

Convert a roof area into roofing squares and shingle bundles, adjusted for pitch and waste, with an optional material cost.

Turn a roof rise and run into pitch, slope angle, the rafter length per foot of run and the area multiplier.

Size rain gutters and downspouts from the roof area, pitch and your design rainfall intensity: K-style or half-round size, number of downspouts, capacity check per downspout and a materials list.

Estimate soffit panels and fascia board from the roof perimeter and overhang, with waste and an optional material cost.

Estimate siding for a whole house: wall and gable area minus doors and windows, squares with waste, vinyl boxes, lap boards or panel sheets, plus corner posts, starter strip, J-channel, house wrap, nails and an installed cost.

Count the bricks or blocks for a wall — rectangle, gable end or total area — from the brick size, mortar joint, number of wythes, openings and waste, with mortar volume and bags, sand, courses, wall ties, pallets and the material cost.

Estimate the bags of mortar and cubic feet needed to lay a given number of bricks or blocks, including the sand.

Work out the cubic yards and tons of crushed stone or aggregate for an area at a chosen depth, with cost.

Find the cubic yards and bags of topsoil, mulch or compost for a bed at a chosen depth, with a cost estimate.

Count the pavers plus the sand and gravel base for a patio, from its area and paver size, with waste and cost.

Calculate the grout or concrete needed to fill the cores of a CMU block wall, in cubic yards and 80 lb bags.

Estimate studs, top and bottom plates and total lumber for a framed wall from its length, spacing and openings.

Work out how many 4×8 plywood or OSB sheets cover a wall, floor or roof area, with waste allowance and material cost.

Get the concrete volume for a slab plus the rebar for a grid — total bar length, number of bars each way, and tie count.

Estimate concrete for a continuous strip (wall) footing from its total run, width and depth — cubic yards and 60/80 lb bags.

Find the concrete to set fence posts — hole volume minus the post, cubic feet per hole and total 50 lb bags for the run.

Calculate the bedding sand under a paver patio — cubic yards for a chosen sand depth, plus tons and how many bags.

Estimate the drainage gravel for a French drain trench — cubic yards and tons after subtracting the perforated pipe.

Find the water volume of a round culvert or pipe — full or at any fill depth — in cubic feet, gallons and water weight, plus its Manning flow capacity from the slope and pipe material, with a depth-by-depth table and common culvert sizes.

Size the gravel base trench for a segmental retaining wall — trench depth, base gravel in cubic yards and tons.

Count suspended ceiling tiles and grid for a room — full tiles, border cuts, main runners, cross tees and wall angle.

Get the miter and bevel saw angles to cut crown molding flat on a compound saw for any wall corner and spring angle.

Price rough lumber by the board foot — total board feet for a stack of boards and the cost at a per-board-foot rate.

Estimate the fasteners for a job from the number of joints and fasteners per joint — total count, boxes to buy and cost.

Estimate the studs, top and bottom plates and drywall sheets for a framed wall from its length, height and stud spacing.

Count the floor joists for a room and check whether your joist size spans the distance at your chosen on-center spacing.

Common rafter length from the run or building span and the pitch (x/12, degrees, percent or total rise), with the ridge board deduction, sloped overhang tail, plumb and seat cut angles, birdsmouth heel and height above plate, the board length to buy, rafter count and an optional hip or valley rafter.

Calculate the cubic yards of concrete for a solid poured staircase from the step count, rise, run and width, plus bag counts.

Get a rough built-up header size and the number of jack studs for a window or door opening from the span and what the wall carries.

Estimate the grout weight and tile spacers for a job from the tile size, joint width and area covered.

Count the 4×8 subfloor sheets of plywood or OSB for a floor, with waste, plus the adhesive and screws to fasten them.

Work out the square footage of poly vapor barrier for a crawlspace, wall or slab — including overlap — and the number of rolls.

Find how many downspouts a roof needs based on the drained roof area and the total length of gutter run.

Calculate the ridge vent length an attic needs for balanced ventilation from the attic area and the required net free area.

Count the concrete blocks and mortar bags for a foundation or basement wall from its length, height and courses.

Work out how many footings and posts a deck needs from its size and the maximum post and beam spacing.

Find the concrete volume for round columns or piers from diameter, height and count — in cubic yards, cubic feet and bags.

Estimate concrete for a combined curb and gutter run from the cross-section dimensions and length — in cubic yards and bags.

Find how much concrete a Sonotube pier takes from tube diameter, depth and count — in cubic yards, cubic feet and bags.

Estimate how many bags of mortar mix a brick job needs from the brick count and bricks-per-bag yield, with a waste allowance.

Lay out vertical and horizontal rebar in a concrete block wall from the wall size and bar spacing — bar counts and total length.

Estimate bags of floor leveling compound from the area and average fill depth, using each bag’s cubic-foot yield.

Estimate bags of thinset mortar for a tile job from the area and the trowel size your tile calls for.

Estimate bags of self-leveling underlayment from the pour area and minimum thickness, using each bag’s cubic-foot yield.

Find how many rolls of roofing underlayment a roof needs from its area and the coverage of felt or synthetic rolls.

Estimate rolls of house wrap from the building perimeter and wall height, with an overlap allowance and roll coverage.

Count how many insulation batts a wall needs from its length and height, stud spacing and batt length.

Estimate the screws (or nails), joint compound, tape and corner bead for a drywall job from the board area or the number of sheets — with framing and screw spacing, walls vs ceilings, compound type, finish level and the material cost.

Find the copper wire gauge for a circuit from the amps, one-way run length and allowed voltage drop — the larger of the ampacity size and the voltage-drop size.

Check the NEC conduit fill percentage for EMT from the conductor size and count, and see how many wires of that size the conduit can legally hold.

Size the circuit breaker for a load from its watts and voltage, applying the NEC 125% continuous-load rule and rounding up to a standard breaker.

Estimate a home’s total electrical service load with the NEC standard method — general lighting demand plus appliances — and the service amps at 240 V.

Convert between watts, amps and volts on a DC or resistive circuit, and get the resistance in ohms, from any voltage and current.

Calculate three-phase power from line voltage, line current and power factor — apparent kVA, real kW and reactive kVAR.

Convert kVA to amps for single-phase or three-phase systems at any voltage — the current a transformer or generator rating delivers.

Size a backup generator for a house from total running watts plus the surge of the largest motor, with headroom — running and starting watts and recommended kW.

Size an off-grid battery bank from daily energy use, days of autonomy, depth of discharge and system voltage — the amp-hours and usable capacity you need.

Convert an old incandescent bulb’s wattage to the equivalent LED wattage by matching lumens, and see the energy saved.

Find the safe amp rating of an extension cord from its gauge and length, limited by conductor ampacity and a 5% voltage drop, and check it against your load.

Calculate an electric motor’s full-load amps (FLA) from horsepower, voltage, efficiency and power factor for single-phase or three-phase, plus the 125% conductor size.

Estimate the water flow in GPM a pipe can carry from its inside diameter, length and the available pressure, using the Hazen-Williams equation.

Find how many gallons of water a pipe holds from its inside diameter and length — useful for sizing purges, flushes and chlorination doses.

Calculate friction pressure loss in a water pipe from flow rate, diameter, length and material using the Hazen-Williams equation.

Work out how long a tank, cistern or pool takes to fill from its volume or its dimensions and the flow rate, or solve for the flow rate you need or the water added in a set time, with a partial fill, water drawn off while filling, finish time and a fill-progress table.

Water heater recovery rate and reheat time for electric, gas and heat-pump tanks: element kW or burner BTU/h, tank size, temperature rise or inlet and setpoint temperatures (°F or °C), part-tank reheats, estimated first-hour rating, energy and cost per reheat, and a recovery table by season.

Size a water pump: find the hydraulic and brake horsepower needed to move a given flow against a given total head.

Estimate the total dynamic head and horsepower a well pump needs from the water depth, desired house pressure and peak demand.

Work out the fall of a drain or sewer line — total drop, slope from a measured drop or two invert elevations, or the longest run your available drop allows — and check it against the IPC/IRC or UPC minimum slope for the pipe size, with flow velocity, full-pipe capacity and a drop-by-station table.

Size a sump pump from how fast water rises in the pit — turns the inflow into GPM and GPH with a safety margin.

Check whether an irrigation zone fits your water supply — total zone demand in GPM and the maximum number of heads per zone.

Compare the total installed cost of PEX and copper repiping — materials plus labor per foot — and see the savings.

Estimate a home’s peak hot-water flow in GPM by adding up fixture units and applying the demand (Hunter) diversity curve.

Estimate the cooling BTU/hr a room needs — by the BTU-per-square-foot rule or the ENERGY STAR room-size chart — from its area or length × width, ceiling height, occupants, sun, insulation, climate and kitchen use, with tons, kW, the unit size to buy, power draw and running cost.

Estimate a room or home heating load in BTU/hr from area, ceiling height, climate and insulation, then size the furnace input for its AFUE.

Size a heat pump in tons from your home area and climate, and estimate how much supplemental heat you may need on the coldest days.

Work out how much airflow (CFM) a room’s ducts should deliver from the system tonnage and the room’s share of the conditioned area.

Find the round duct diameter — and equivalent square duct — needed to carry a given airflow at a chosen air velocity.

Compare the yearly cooling cost of an old and a new air conditioner or heat pump by SEER or SEER2 rating, with heating savings by HSPF, payback on the new unit, lifetime savings, CO₂ avoided and savings at other ratings and climates.

Size a ductless mini-split head for a single zone from its area, insulation, sun and occupancy, and match it to a standard capacity.

Size a radiator to a room’s heat loss and convert the BTU/hr to square feet of equivalent direct radiation (EDR) for steam or hot-water systems.

Add up duct friction and component pressure drops to estimate a system’s total external static pressure and compare it to the blower rating.

Get a typical suction and liquid line size for a split AC or heat pump by tonnage, with a note on long line-set runs.

Find the fresh-air ventilation rate a home needs in CFM using the ASHRAE 62.2 formula from floor area and bedroom count.

Turn an airflow and the grains-of-moisture difference between outdoor and indoor air into a latent cooling load and daily water removal.

Find the cubic yards and ready-mix cost for a concrete driveway from its length, width, thickness and price per yard.

Calculate the concrete for a sidewalk or walkway in cubic yards and bags from its length, width and thickness.

Work out the concrete for a patio slab in cubic yards, bags and ready-mix cost from length, width and thickness.

Calculate the concrete for round deck footings from their diameter, depth and count — in cubic yards and bags.

Count the precast pier blocks for a deck or shed floor from its size and the spacing between piers along and across the beams.

Count the 8×8×16 blocks for a wall plus the mortar bags and vertical rebar it needs, from the wall length and height.

Estimate the flat stone veneer square footage and corner pieces for a wall, minus window and door openings, with waste.

Estimate the tons of flagstone and cost for a patio from its size and the coverage per ton, with waste included.

Calculate the gravel for a compacted base in cubic yards and tons from the area and how deep you want the base.

Work out the concrete for a cast countertop in cubic feet and 80 lb bags of countertop mix from its length, width and thickness.

Estimate the stucco for a three-coat wall — base and finish bags — from the wall area minus openings, with waste.

Count the bricks for a chimney from its width, depth and height, plus mortar bags — for a hollow rectangular stack.

Work out how many metal roofing panels you need from the roof area or from the roof length, width and pitch: panels per side, cut lengths or stock lengths with end laps, linear feet, screws or standing-seam clips, ridge, eave and rake trim, closures, underlayment and cost.

Count the concealed clips and fasteners a standing-seam metal roof needs from panel count, panel length and clip spacing.

Estimate asphalt shingle bundles from roof area with a proper waste allowance and a separate starter-strip count along the eaves.

Count hip-and-ridge cap shingle bundles and individual caps from total ridge and hip length, exposure and waste.

Find the true diagonal length of a roof valley from the horizontal run and pitch, plus how many flashing pieces to buy.

Total the drip edge for your eaves and rakes and convert it to 10-foot pieces, accounting for the overlap at each joint.

Estimate rolls of ice-and-water shield for the eaves and valleys from run length, coverage width and roll size.

Size attic intake and exhaust ventilation with the 1/300 net free area rule, then convert it into a vent count.

Lay out the rough opening, headers, trimmers and interrupted rafters for framing a skylight into a rafter roof.

Convert your total gutter run into gutter-guard sections and estimated cost, with a waste allowance for corners and cuts.

Find the peak roof runoff and how many downspouts you need, sized to your roof area, local rainfall intensity and downspout type.

Convert ground snow load to a flat-roof design snow load using the ASCE 7 factors, and get the total load on your roof.

Estimate a starting welding amperage from material thickness using the one-amp-per-thousandth rule, adjusted for the metal you are joining.

Work out how many stick electrodes a fillet weld will burn from the weld length, leg size and deposition efficiency.

Convert a target MIG amperage and wire diameter into a wire feed speed in inches and metres per minute as a starting setting.

Estimate how much shielding gas a job uses and how long a cylinder lasts from the flow rate and arc-on time.

Compute the cross-section, volume and weld-metal weight of an equal-leg fillet weld from its leg size and length.

Find the deposition rate of a MIG or wire process in pounds and kilograms per hour from wire feed speed, wire size and efficiency.

Calculate welding heat input and arc energy in kJ/mm, kJ/in and J/in to AWS D1.1, ASME IX or EN 1011-1. Use average volts and amps, a timed run, or the instantaneous energy or power method for pulsed and waveform-controlled welding. Checks a WPS window, solves the travel speed to hit it, and estimates the t8/5 cooling time.

Estimate a minimum preheat temperature for carbon steel from its carbon equivalent and section thickness, as an educational guide.

Calculate the weight of steel, stainless, aluminum, copper or brass stock — plate, bar or tube — from its dimensions.

Calculate bend allowance, bend deduction and flat length for a sheet-metal bend from thickness, inside radius, angle and K-factor.

Find how many pieces you can cut from a stock length, and how many bars a job needs, once saw kerf and end trim are counted.

Estimate the kerf offset, material removed and dimensional loss when plasma or laser cutting, so parts come out to size.

Work out how much paint you need from the wall area, number of coats and paint coverage.

Estimate how many rolls of wallpaper you need from your room perimeter, wall height and roll size.

Estimate the cubic yards and tons of gravel needed to cover a driveway to a given depth.

Estimate how many deck boards and how much linear footage you need for a deck.

Find how many fence posts, sections, rails and pickets or panels you need — for one straight run or several sides with corners and gates — plus the post length, hole size, bags of concrete, gravel and the material cost.

Estimate how many drywall sheets you need for a given wall and ceiling area.

Estimate how many blocks you need to build a retaining wall of a given length and height.

Find how many boxes of laminate or vinyl plank flooring you need for one room or several, from the box coverage or the plank size, with waste by layout, underlayment rolls, trim and transitions, a row-by-row plank layout check and the total cost.

Friction head loss and pressure drop in a water pipe from flow rate, diameter, length and material (Hazen-Williams C) — plus velocity, fittings allowance and the pipe size that keeps velocity under 1.5 m/s.

Size a rain garden or bioretention bed from the roof or paved area draining to it, soil type and ponding depth — surface area, volume captured from a design storm, dimensions and drain-down time.

Miter and blade-bevel settings for compound cuts — crown moulding (spring angle 38° or 45°), picture frames, boxes and planters with sloped sides — for any corner angle, with flat and nested cutting methods.

Drill bit sizes for wood screws by gauge or metric diameter — pilot hole in softwood and hardwood, clearance (shank) hole and countersink — with fractional, letter/number and metric bit equivalents and tapping-drill sizes for machine screws.

Correct drill press or hand-drill rpm from bit diameter and material — twist drills, brad-point, Forstner, hole saws and spade bits in wood, aluminium, mild steel, stainless and plastics — from recommended surface speeds.

Taper angle and jig settings for furniture legs from top and bottom dimensions and taper length — plus the compound splay angle, cut angle for angled tenons and the floor footprint of splayed legs.

How many clamps a glue-up needs from joint area, wood species and glue type — recommended clamping pressure (PVA on softwood to hardwood), force per clamp, spacing and open/clamp times.

Cubic-inch box fill for a junction or device box from the number and gauge of conductors, devices, clamps, grounds and fittings — NEC 314.16 volume allowances — with standard box sizes that comply.

Minimum copper or aluminum wire size for a load from NEC Table 310.16: 60/75/90 °C insulation, termination rating, ambient temperature and rooftop correction, more-than-three-conductor adjustment, 125% continuous load, small-conductor breaker limits, parallel sets and a voltage-drop check, with the breaker size and a comparison table.

Minimum septic tank size from bedrooms under eight labelled US code tables (common table, California/UPC-style, New York, Washington, Virginia, Massachusetts Title 5, Florida, Arizona) or from occupants and daily flow, with garbage-disposal allowance, standard tank size, retention time, two-compartment split, pump-out interval, a check of an existing tank and a rough drain-field area by soil.

Leach field trench area and length from daily wastewater flow and soil percolation rate — soil application rates by texture or perc test, trench width, number of laterals and a gravel-less chamber equivalent.

Superheat and subcooling for R-410A, R-32, R-22, R-134a and R-454B systems from suction/liquid pressures and line temperatures — target superheat for fixed-orifice systems from indoor wet-bulb and outdoor dry-bulb, with charge diagnosis.

Ventilation airflow for a room from its size and target air changes per hour — recommended ACH by room type (kitchen, bathroom, office, classroom, lab, hospital), CFM, m³/h and L/s, the ACH your fans deliver after duct losses, contaminant clearance times, HVI bathroom sizing and ASHRAE 62.1 outdoor air per person.

Earthwork volumes between survey stations by the average-end-area method — cut and fill cross-section areas at each station, prismoidal correction, swell and shrinkage factors, truck loads and net import/export.

Total R-value and U-factor of a wall, roof or floor assembly from its layers (with typical material R-values), heat loss in watts and BTU/h for a given area and temperature difference, annual energy and cost, and the effect of adding insulation.

Effective R-value and U-factor of a wood or steel stud wall once the framing is counted: parallel-path method with ASHRAE framing factors (25% at 16 in, 22% at 24 in), steel-stud correction factors, the R lost to thermal bridging, how much continuous insulation wins it back, RSI and W/m²K, and a 2021 IECC U-factor check.

Will condensation form on a window or cold wall? Inside-surface temperature from the U-factor and indoor/outdoor temperatures, compared with the dew point of the room air — the safe indoor humidity, the outdoor temperature at which dripping starts, and mould-risk thresholds.

Steady-state indoor CO₂ concentration from occupancy, activity and outdoor-air ventilation rate, the outdoor air needed per person to hold a CO₂ target (800, 1,000 or 1,200 ppm), ASHRAE 62.1 minimums by space type, and how long a room takes to reach equilibrium.

Estimate the sound transmission loss of a wall or floor from its mass (mass law), the approximate STC/Rw rating, the boost from double-leaf construction with an air gap and insulation, the noise reduction between rooms and what will still be heard.

Size an evaporative cooler by CFM from room volume and air changes, predict the outlet air temperature from outdoor dry-bulb and humidity (media effectiveness), water consumption per hour, the temperature drop you can expect and whether your climate suits evaporative cooling.

Solar heat entering through a window from its area, orientation, SHGC and shading — peak watts and BTU/h, the cooling load it adds in tons, daily energy on a sunny day, and how much low-SHGC glass, overhangs or exterior shades would cut it.

Bending math for EMT and rigid conduit: distance between bends for an offset at 10°, 22.5°, 30°, 45° or 60° (multipliers and shrink), three-point and four-point saddle marks, and the travel of a kick — with the shrink to subtract before the first mark.

Total dynamic head for pump selection: static lift and discharge elevation, outlet pressure (psi, bar or kPa) minus any source pressure, Hazen-Williams pipe friction for Schedule 40, Schedule 80 or a custom pipe, fittings as a percentage or counted one by one, velocity head, specific gravity, NPSH available, a system curve, water and brake horsepower, motor size and running cost.

Net positive suction head available from atmospheric pressure at altitude, liquid temperature (vapour pressure), suction lift or flooded suction and suction-line friction — compared with the pump’s NPSH required, with the margin, the maximum safe lift and hot-water limits.

Predict flow, head/pressure and power at a new speed or impeller diameter with the affinity laws — new duty point from a known one, rpm needed for a target flow or head, energy saving from slowing down, and the limits of the laws.

Size a potable-water or hydronic expansion tank in gallons or litres: water or glycol expansion between fill and maximum temperature (°F or °C), required acceptance volume, acceptance factor from the fill pressure and maximum pressure (psig, bar or kPa), wrong pre-charge effects, the next standard tank, peak pressure for each tank size, a candidate tank check and a suggested hydronic fill pressure from building height.

Peak pressure rise from suddenly stopping flow in a pipe (Joukowsky equation) from velocity, pipe material and size — wave speed, critical closure time, the pressure at the pipe versus its rating, and how slower valve closing or an arrestor reduces it.

Drawdown of a bladder or diaphragm well pressure tank from its total volume and the pump cut-in/cut-out settings, the tank size for a minimum pump run time at your pump’s flow, pump cycles per hour, pre-charge pressure and a check of a chosen tank.

Tap drill size for metric (M coarse and fine) and unified (UNC/UNF) threads: pick a standard size or enter the diameter and pitch or TPI, choose the thread percentage, and get the exact drill, the nearest metric, fractional, letter and number drills with the thread % each gives, form-tap drills, clearance holes and blind-hole drill depth. It also works in reverse, giving the thread % for a drill you already have.

Milling speeds and feeds in metric or inch: spindle rpm from surface speed, table feed from chip load with radial, ball-nose and lead-angle chip thinning, average chip thickness, material removal rate, spindle power, torque and cutting force, spindle load, cycle time and a stepover table.

Theoretical and practical surface roughness of a turned or faced part from feed per revolution and insert nose radius (mm or inch): Ra, Rz, exact Rt and RMS in µm and µin, the ISO N grade, the feed or nose radius needed for a target Ra or Rz, wiper-insert estimates, rpm and cutting time, and a feed-versus-finish table and chart.

Peak stormwater runoff Q = C·i·A for a site from area, runoff coefficient by surface type and design rainfall intensity — composite C for mixed surfaces, flow in cfs and L/s, the pipe or culvert size to carry it and the volume of a design storm.

Manning’s equation for trapezoidal, rectangular, triangular and part-full circular channels: solve for discharge, normal depth, slope or bottom width, with velocity, Froude number, critical depth and slope, shear stress, an erosion check and a rating table.

Discharge over a sharp-crested rectangular weir (suppressed or contracted), a V-notch (triangular) weir or a Cipolletti trapezoidal weir from head and crest dimensions — cfs, L/s and gpm, the head for a target flow, and the rating table.

Flow through a submerged orifice or tank outlet from diameter, head and discharge coefficient (Q = C·A·√(2gh)) — cfs, gpm and L/s, the orifice size for a target release rate (detention pond control), jet velocity, and time to drain a tank between two levels.

Find the ramp length for any rise at 1:12 or a gentler slope, or check the slope of an existing ramp against the 2010 ADA Standards: runs and landings, straight, L-shaped or switchback footprint, sloped length, handrail length, deck area and a run-by-run layout.

Formwork contact area and materials for footings, walls, columns and slab edges — square feet of forms, plywood sheets, studs/walers or 2× lumber, form ties, oil, and reuse cycles, with labour hours from typical productivity rates and the per-square-foot cost.

Frame scaffold materials for a wall or façade: number of frames, cross braces, planks or decks, base plates, guardrails and toe boards from length, working height and bay size — lifts, weight on the ground, tie-ins, and rental cost per week.

Tension in each leg of a two-, three- or four-leg sling from load weight, sling angle or leg length and spread, the load-angle factor, required sling rating with design factor, headroom needed, and the effect of an off-centre centre of gravity.

Design wind pressure from wind speed with velocity pressure, exposure/height factor and force coefficient — psf and kPa, total force on a sign, fence, solar array or wall, overturning moment at the base, and the post/footing implications.

Carbon equivalent calculator for steel weldability: IIW CE and Ito-Bessyo Pcm from the mill certificate chemistry, hardenability rating, and a recommended preheat temperature band from CE and combined plate thickness for low-hydrogen welding.

Shielding gas calculator for MIG and TIG: gas used per shift from flow rate and arc-on time, how long a cylinder lasts, cylinders needed for a job, gas cost per hour of arc time and per metre of weld, with allowances for pre/post-flow and leaks.

Calculate weld metal volume and filler wire or electrode weight for single-V, double-V and square butt joints from plate thickness, bevel angle, root gap, root face and reinforcement, with deposition efficiency by process and cost of consumables.

Welding machine duty cycle calculator: how many minutes in ten you can weld at a given amperage, the allowable current for continuous welding, the duty cycle at any other output using the rated-current relationship, and the cool-down needed.

Estimate weld shrinkage and distortion for butt and fillet welds: transverse shrinkage (0.2 Aw/t + 0.05 d), longitudinal shrinkage, angular distortion and edge lift, fillet flange warpage against the AWS D1.1 limit, beam camber, groove-area from bevel geometry, cut-length allowances and presetting angles.

Size a septic leach field from a percolation test: perc rate in minutes per inch converted to a soil application rate, design daily flow from bedrooms or occupants, required absorption area, trench length for a chosen trench width, and the number of laterals.

Add up water supply fixture units for a building, convert WSFU to probable peak demand in gpm with the Hunter curve, and pick the service or branch pipe size that keeps velocity under 8 ft/s (5 ft/s for hot water), with the flow each copper size carries.

Size an on-demand water heater from simultaneous fixture flow and the temperature rise from your groundwater temperature: required BTU/h input for gas units (with efficiency), kW and amperage for electric units, and the flow a given unit delivers at your temperature rise.

Calculate the hot-to-cold mixing ratio a thermostatic mixing valve uses to deliver a set outlet temperature, the hot water flow drawn from the tank at a given outlet flow, how many gallons of mixed water a storage tank provides, and the scald and Legionella temperature context.

Calculate the water pressure lost or gained per floor or metre of elevation (0.433 psi per foot), the residual pressure at the highest fixture after elevation, meter, backflow and friction losses, and the booster pump head needed to deliver a target pressure.

Estimate the standby heat loss of a hot water recirculation loop from pipe length, size, insulation and temperatures, the annual energy cost by fuel, the pump electricity, savings from insulation or a timer/demand control, and the water and wait time saved versus no recirculation.

Fire sprinkler hydraulic calculator: design density and remote area by NFPA 13 hazard class, flow per head from the K-factor and pressure (Q = K√P), minimum pressure for the required density at a given head spacing, number of heads in the design area, total system demand with hose allowance and duration, and tank volume.

Analyse a fire hydrant flow test: discharge from the pitot pressure and outlet size (Q = 29.83 c d² √P), the available flow at 20 psi residual using the NFPA 291 Hazen–Williams exponent 0.54, flow at any other residual pressure, the supply curve, and hydrant colour class.

Calculate the occupant load of a room or floor from area and the IBC/NFPA 101 occupant load factor, the number of exits required, the total egress width for doors and stairs (0.2 and 0.3 inch per person), the capacity of your existing doors and whether a sprinkler system changes the numbers.

Apply the fan laws: change fan speed and see the new CFM, static pressure and brake horsepower (∝ rpm, rpm², rpm³), find the rpm needed for a target airflow, the pressure and power that follow, the effect of air density, and pulley size to hit the new speed.

Use the sensible heat equation to find delivered BTU/h from airflow and temperature split, the CFM from heat and ΔT, or the ΔT to expect, plus CFM per ton, the 350–450 CFM per ton check, kW output, altitude correction and a table of splits by airflow.

Convert a blower door test result to air changes per hour at 50 Pa (ACH50), CFM50 per square foot of envelope, equivalent leakage area, estimated natural infiltration with the LBL N-factor, compare with code tightness targets (IECC 3 or 5 ACH50, Passive House 0.6) and see when mechanical ventilation is required.

Find the mixed air temperature entering a coil from return and outside air temperatures and the outside-air percentage, or back-calculate the outside air fraction from three measured temperatures, with the minimum OA damper position, freeze-stat risk, economizer check and mixed-air enthalpy.

Find the thermal balance point where a heat pump's output equals the house heating load as outdoor temperature falls, using the design heat loss and the heat pump's capacity at 47 °F and 17 °F, plus the auxiliary heat needed at design temperature, the economic balance point versus gas or resistance heat, and hours below the balance point.

Find the maximum allowable span for deck joists by lumber species, size and spacing from the IRC deck joist span table, check your planned span, see the allowed cantilever, the smallest joist that works, and the number of joists for the deck width.

Determine the maximum deck beam span (post spacing) for built-up 2-ply and 3-ply beams from the IRC beam span table based on the joist span it carries, check your planned post spacing, find the smallest beam that works and the number of posts needed.

Size deck post footings from the tributary area each post supports, the design live and dead load, soil bearing capacity and footing shape (round or square), with the IRC R507.3 minimum footing sizes, concrete volume per footing and frost-depth reminder.

Get the on-centre spacing for ½ inch lag screws or through-bolts fastening a deck ledger to the house band joist from the IRC ledger fastener table by joist span, with stagger pattern, edge distances, total fastener count for the ledger length and the rule against fastening through brick or stucco.

Size a simply supported wood beam or header under a uniform load: bending moment, required section modulus from allowable bending stress, deflection check against L/360 or L/240, shear check, and the smallest standard sawn or built-up lumber size that passes.

Lay out a cut stair stringer from total rise: number of risers and treads, exact riser height and tread run within code (max 7¾ inch rise, min 10 inch run, 2R + T rule), stringer length and lumber size, throat depth check for a 2×12, the number of stringers by tread width, and the top-step drop for finished flooring.

Zonal-cavity lumen method: number of luminaires needed for a target illuminance from room size, fixture lumens, coefficient of utilization from the room cavity ratio and surface reflectances, and light loss factor, with the resulting average lux/foot-candles, layout grid and watts per square foot.

Calculate lighting power density in watts per square foot and per square metre from installed fixture wattage and floor area, compare with ASHRAE 90.1 / IECC space-by-space allowances by occupancy type, and see the annual energy cost and the savings from controls.

Estimate the average daylight factor of a room from glazed area, visible light transmittance, sky angle, room surface area and reflectance (Lynes/BRE formula), the interior lux it gives under a standard overcast sky, the glazing needed for a target daylight factor and the daylit depth rule of thumb.

Find the buildable envelope of a rectangular lot after front, rear and side setbacks, the maximum footprint under a lot coverage limit, impervious surface limits with driveway and patio, the largest house that fits, and whether a proposed footprint complies.

Calculate a site's impervious percentage and weighted runoff coefficient from roofs, paving, gravel, lawn and woods, the extra runoff volume a storm produces compared with the undeveloped site, the detention or rain-garden volume to capture it, and a stormwater fee estimate.

Build the gross load for a crane lift — load, rigging, block, jib and hoist line deductions — compare it with the load chart capacity at the working radius, get the percentage of capacity and critical-lift flag, the radius change from boom angle, and ground bearing under the load.

Estimate the maximum load on a mobile crane outrigger from the crane weight, counterweight, boom and gross load, the ground bearing pressure under the float and under a timber or steel mat, the mat size needed for the allowable soil bearing pressure, and the rule-of-thumb 85% single-outrigger case.

Up-peak elevator traffic analysis: round-trip time, five-minute handling capacity, interval, average waiting and transit time and the number of cars needed for an office, residential, hotel or hospital building — from population or floor area, floors, floor height, car size, speed, door times and an express zone.

Size a sloped or benched trench to OSHA 1926 Subpart P: maximum allowable slope for soil type A, B or C, top width for a given depth and bottom width, excavation and spoil volume with swell, spoil pile setback, and when a trench box or shoring is required instead.

Choose a roll-off dumpster size from the debris you have — roofing squares, drywall, lumber, concrete, brick, dirt, mixed remodel waste, furniture — with the volume in cubic yards, the weight in tons, the container weight limit check, overage charges and how many hauls you need.

Estimate the debris from demolishing a house or building using the standard volume formula (L × W × H × 0.33 ÷ 27) and weight factors by construction type — wood frame, masonry, steel, concrete — with roll-off counts, truck loads, recycling diversion and landfill tipping cost.

Calculate the weight and volume of roofing debris from a tear-off by roof area, number of layers and material — 3-tab, architectural, tile, slate, metal, wood shake, built-up — with underlayment and flashing, the dumpster size and weight allowance, and disposal cost per square.

Estimate construction and demolition waste from floor area and project type using EPA generation rates (new build 3.9–4.4 lb/ft², renovation, reroof, demolition up to 155 lb/ft²): tons by material, loose cubic yards, roll-off count, diversion needed for a 50, 65 or 75% target and tipping cost.

Calculate the weight of a concrete slab, driveway, patio or wall being removed, the loose volume after breaking with swell, whether rebar or mesh is present, truck and dumpster loads, disposal or recycling cost, and the breaking time with a jackhammer or excavator.

Check a chimney for a wood stove or open fireplace: flue area from the fireplace opening (IRC round 1/12, square 1/10, rectangular 1/8 rules or the height-based rule), flue size against a stove collar (no more than 3× its area, 2× for an exterior chimney), the smallest round or clay liner that works, minimum height by the 3-2-10 rule from the roof rise or pitch, and theoretical draft from height, flue and outdoor temperature and altitude.

Work out wood stove clearances to combustible walls with and without a ventilated heat shield, the hearth pad (floor protector) size from the stove footprint and the front, side and rear extensions (US 16 in, Canada 18 in), the shield size, the floor space the installation takes and the stovepipe clearance.

Size a dado, groove or rabbet for real plywood and MDF: the actual thickness behind the nominal size (23/32 for "3/4", 18 mm Baltic birch), snug, exact or slip fit, depth from the housing board, the stacked dado chippers and shims to use, the right undersized router bit or a two-pass fence offset, and the wood left behind the joint.

Design a French cleat for cabinets, tool walls or heavy mirrors: the two cleat sizes from a 45° rip, how many studs or anchors the wall cleat catches, screw length through the drywall, a conservative safe-load check, the lift needed to unhook, the bottom spacer and cleat-wall spacing.

Size a drawer box from the cabinet opening — width, height and depth clearances for side-mount ball-bearing, undermount (Blum-type) and wooden runners, the slide length to buy, and a full cut list for the sides, front, back and bottom from your material thickness and bottom groove.

Size a kitchen range hood — CFM from the cooktop's BTU output for gas or the width for electric, the island multiplier, duct diameter for the airflow, the loss from duct length and elbows, when make-up air is required (over 400 CFM in most US codes) and the sone level to expect.

Size a bathroom extractor fan by the HVI area rule (1 CFM per square foot, 50 CFM minimum), the fixture rule for large bathrooms (50 CFM per toilet, shower or tub, 100 for a jetted tub) and the 8 air-changes-per-hour method, with duct derating, sone rating and timer or humidistat run-time advice.

Size a whole-house fan by air changes per hour (5–40 ACH) or by 2–3 CFM per square foot, split it across several fans, check the attic net free vent area it needs (1 ft² per 750 CFM) from your vents, the window area to open (4 ft² per 1,000 CFM), minutes per air change, and the running cost, savings and payback against air conditioning.

Design underfloor heating for a room — required output in W/m² from insulation level or a known heat loss, the floor surface temperature check (EN 1264 curve) against the 29 °C or 27 °C limit, the mean and flow water temperature for your floor finish, construction and heat source, wet-system pipe length, loops and flow per loop for 12/16/20 mm pipe at 100/150/200 mm spacing with a materials list, or electric mat wattage, current and running cost, in metric or US units.

Calculate the U-value of a wall, roof or floor from up to six layers — pick materials from a list or enter λ, in mm or inches — with surface resistances, air cavity, timber or steel-stud bridging (ISO 6946 combined method), air-gap correction, R-value in SI and imperial, heat loss and yearly energy, a temperature profile with surface-condensation check, UK, Passivhaus and Spanish CTE comparisons, and the insulation needed to reach a target.

Check a bolted connection to Eurocode 3 (EN 1993-1-8) or AISC 360 LRFD/ASD — tension and shear resistance of M6–M36 and 1/2–1-1/2 in bolts in grades 4.6 to 12.9, A307, A325 and A490, single or double shear, threads in or out of the shear plane, combined loading, plate bearing and tear-out, slip resistance, edge distances, preload and tightening torque, and how many bolts the load needs.

Size an electric fence charger: total wire length from fence length and number of hot strands, output joules needed for your vegetation load and animal (cattle, horses, sheep and goats in wool, pigs, poultry netting, predator exclusion), the stored-joule rating to buy, ground rods required, wire, insulators and posts, and battery or solar sizing for a remote energizer.

How many acoustic panels does a room need? From the room size, its current reverberation (measured or estimated from finishes) and the RT60 target for its use — home studio, podcast room, home theater, office, classroom, restaurant, church — get the absorption to add in sabins, the number of 2×4 ft panels by thickness and NRC, wall coverage percentage, bass-trap advice and cost.

Design tiered seating where everyone sees the stage or screen: from the focal point, first-row distance, row depth and target C-value, get the floor height and riser of every row as a true sightline curve, uniform risers or 2–6 constant-riser flights, with staggered seats, riser rounding, a step cap, the C-value each row really gets, the rake angle, back-row view and aisle-step count.

Plan defensible space around a home: the area of Zone 0 (0–5 ft ember-resistant), Zone 1 (5–30 ft) and Zone 2 (30–100 ft) from your house footprint and property line, CAL FIRE tree-canopy and shrub spacing by slope, trees to keep and remove, Zone 0 gravel, upkeep hours and a home-hardening checklist.

How much greywater does your household produce and what can it irrigate? Litres per day from showers, baths, bathroom sinks and laundry (not kitchen or toilets), the garden area it supports by climate and plant type, surge tank and mulch-basin sizing for a laundry-to-landscape or branched-drain system, water and money saved, and what not to put down the drain.

Size a tornado or hurricane safe room from the number of people: FEMA P-361 / ICC 500 floor area per standing, seated, wheelchair and bedridden occupant, usable vs gross area, room dimensions, design wind and debris criteria, doors, ventilation, toilets, water and supplies, and a rough cost.

Size self-regulating or constant-wattage de-icing cable for eaves, gutters and downspouts: cable length from the eave length, overhang and zigzag loop height, extra for gutters and downspouts, total watts and amps per circuit, how many runs a breaker supports, the seasonal electricity cost with a thermostat or snow sensor, and where ice dams really come from.

Size attic ventilation to the 1/150 or 1/300 rule: net free area required for the attic floor area, split 50/50 or 60/40 between low intake (soffit) and high exhaust (ridge, box, turbine or gable vents), how many feet of soffit and ridge vent or how many vents that takes with your products’ own NFA ratings, whether your current vents are balanced, rafter baffles and a powered-fan CFM alternative.

Get water away from the house: the drop required over the first 10 feet (6 inches, 5%) and beyond (2%), how much soil or fill it takes to regrade around the foundation, the slope as a percentage, ratio and degrees, when a swale or French drain is needed instead, swale sizing for a roof and yard area, and downspout extension distances.

Size a riding arena and estimate the materials: compacted stone base and screenings by depth, footing sand or sand-fibre mix by depth and density in tons and truckloads, geotextile, perimeter drainage and kickboards, with costs and the standard dressage and jumping dimensions.

Turn a concrete mix ratio (1:2:3, 1:2:4, 1:1.5:3…) and a volume into bags of cement, sand, gravel and water — with the 1.54 dry-volume factor, waste and every nominal mix compared.

Calculate rebar stirrups (ties) for a beam or column: cut length with 135° or 90° hooks, how many stirrups at closer end spacing, total metres, weight in kg and how many 12 m bars to buy.

Estimate a beam and block (joist and hollow block) slab: number and length of precast joists, infill blocks, topping concrete in m³ and welded mesh for any room size, block size and joist spacing.

Size a household water storage tank: daily use by people and habits, the rooftop tank for one day, the cistern or ground tank for several days without supply, and the next standard tank size in litres or gallons.

Work out how much elastomeric, silicone, asphalt or polyurethane roof coating to buy: litres or gallons for the coats you need, 19 L buckets, primer and reinforcing fabric for any roof area.

How much microcement do you need? Kilos of base and finish coats for your floor, wall or countertop area, plus primer, fibreglass mesh and sealer — using per-coat consumption you can match to your product sheet.

How many sheets or rolls of welded wire mesh (6x6 W1.4/W1.4, 6x6-10/10 and heavier) for a concrete slab: layout with laps, total mesh area, weight and rolls of 2.5 × 40 m or 5 × 150 ft.

Estimate concrete compressive strength at 1, 3, 7, 14 or any number of days from its 28-day f′c, using the ACI 209 strength-gain curve for normal or high-early cement, moist or steam cured — in MPa, kg/cm² and psi.

Work out the cement bags and sand for plastering (rendering) a wall from the area, plaster thickness and mix ratio 1:3, 1:4, 1:5 or 1:6 — with the 1.27 dry-volume factor and an allowance for uneven walls.

Calculate the cement bags and sand for a sand-cement floor screed from the floor area, thickness and mix (1:3, 1:4, 1:5), plus the screed weight per m² and the rule-of-thumb drying time.

Find how much loose fill (earth, clay, sand, gravel or crushed stone base) to order for a compacted layer: compaction factor, loose m³ or yd³, tonnes and truckloads.

Calculate the tension development length ℓd and the Class A or Class B lap splice length of a reinforcing bar to ACI 318-19 from bar size, steel grade, concrete f′c, bar position, coating and spacing.

Work out the cutting length of a reinforcing bar — straight, hooked, L-bar, U-bar or bent-up (crank) bar — with bend deductions, weight in kg and how many 12 m stock bars to buy for a bar bending schedule.

Design a segmental or semicircular brick arch: radius from span and rise, arch angle, intrados and extrados lengths, number of bricks per ring (odd, for a keystone) and the tapered joint widths.

Count the gabion baskets for a wall or revetment and the tonnes of stone fill: box size, layout along, across and up, gabion volume, filled density from porosity and the geotextile behind the wall.

Estimate how many sandbags you need for a flood barrier (pyramid levee) of a given length and height, the base width, the tonnes of sand to fill them and bags per metre or foot.

Estimate how many tubes of caulk or sealant you need from the joint length, width and depth — 300 mL cartridges, 10.1 oz tubes or sausages — with the right depth ratio, bead length per tube and backer rod size.

Calculate board feet of open-cell or closed-cell spray foam for an area and thickness, the number of DIY kits or drum sets, the R-value (and metric RSI) and the foam volume.

Estimate a chain link fence: mesh rolls, line posts, terminal (end, corner and gate) posts, top rail, tension bars and bands, fence ties and mesh area from the fence length, height, corners and gates.

Calculate barbed wire for a field or ranch fence: total wire length for the number of strands, rolls to buy, line posts, corner and gate posts, H-brace assemblies and staples.

Design a spiral staircase: number of risers and treads, riser height, angle per tread, tread depth at the walkline, clear width, headroom and floor opening, checked against the IRC spiral stair rules.

Estimate steel studs, tracks, drywall boards, framing screws, drywall screws and anchors for a light-gauge metal stud partition (Durlock, Pladur, Tablaroca systems) from the wall length, height and stud spacing.

Estimate the cost to build a house from its floor area and local cost per m² or ft², finish level, design and permit fees, contingency and tax — with a typical breakdown by construction stage.

Turn the failure load of concrete test cylinders or cubes into compressive strength in MPa, psi and kg/cm², average up to three specimens and compare the result with the specified f′c.

Calculate the ultimate and allowable bearing capacity of a strip, square or circular shallow footing with Terzaghi’s equation from cohesion, friction angle, unit weight, width, depth and factor of safety.

Find the area of an irregular four-sided plot of land from its four sides and one diagonal (two triangles by Heron’s formula) in m², hectares, square feet, acres and square varas.

Count the glass blocks for a wall or window opening and the mortar, spacers, panel reinforcement and expansion strip — for 19 × 19 cm, 24 × 24 cm, 8 × 8″ and 6 × 6″ blocks.

Calculate the dead load (self-weight plus finishes) and live load of a concrete floor slab, the service load and the factored design load 1.2D + 1.6L in kN/m², kg/m² or psf.

Space pendant lights over a kitchen island evenly: how many pendants, distance between centers and from the ends, gap between shades and how high to hang them above the counter — cm or inches.

Calculate the support reactions, maximum shear force and maximum bending moment of a simply supported beam with a point load anywhere on the span plus a uniform load, in kN and m or kip and ft.

Calculate the fixed-end moment, support reaction, tip deflection and rotation of a cantilever beam with an end point load and a uniform load, from span, material E and moment of inertia I.

Solve a two-span continuous beam with uniform loads by Clapeyron’s three-moment equation — moment over the middle support, the three reactions, maximum span moments and shear, in kN·m or kip·ft.

Find the design flexural strength φMn of a singly reinforced rectangular concrete beam to ACI 318 — stress block depth, neutral axis, steel strain, φ factor, minimum steel and a check against your factored moment.

Size a square or rectangular isolated column footing from the service load, any moment and the allowable soil bearing pressure — net bearing, required area, plan dimensions and maximum and minimum soil pressure.

Check a cantilever retaining wall for overturning, sliding and bearing pressure with Rankine active earth pressure and a surcharge — factors of safety, toe and heel pressures and eccentricity per metre of wall.

Calculate active, passive and at-rest earth pressure coefficients (Ka, Kp, K0) with Rankine or Coulomb theory, and the thrust and pressure diagram on a wall with sloping backfill, cohesion and surcharge.

Calculate the primary consolidation settlement of a clay layer from Cc, Cs, initial void ratio and effective stresses — normally or overconsolidated — plus the time for 50% and 90% consolidation from cv.

Calculate a soil’s void ratio, porosity, degree of saturation, dry, saturated and submerged unit weight from its moisture content, specific gravity Gs and bulk or dry unit weight — soil phase relationships.

Calculate the fineness modulus of fine aggregate from a sieve analysis — percent retained, cumulative retained and passing on each sieve, sand classification and the ASTM C33 grading check.

Compute latitudes and departures of a closed survey traverse from azimuths and distances — linear misclosure, relative precision, Bowditch (compass rule) adjustment, coordinates and enclosed area.

Convert a surveying quadrant bearing such as N 45°30′ E or S 20° W into an azimuth, or an azimuth back into a bearing — in degrees, minutes and seconds, with back bearing and back azimuth.

Calculate the elements of a circular horizontal curve — tangent length, curve length, long chord, external and middle ordinate, degree of curve, PC and PT stations and a deflection-angle stakeout table.

Calculate a parabolic vertical curve from the two grades, curve length and PVI — BVC and EVC stations and elevations, high or low point, K value, elevation at any station and a table of curve elevations.

Calculate storm runoff depth and volume with the SCS / NRCS curve number method — potential retention S, initial abstraction Ia, antecedent moisture adjustment and the updated 0.05 Ia ratio, in mm or inches.

Estimate a catchment’s time of concentration from the flow path length, elevation drop and area with the Kirpich, Témez and Bransby-Williams formulas — the storm duration used in the rational method.

Calculate the flow rate and velocity in a partially full circular pipe with Manning’s equation — full-pipe capacity, Q/Qfull and V/Vfull, hydraulic radius, Froude number and a self-cleansing velocity check.

Calculate the design water demand of a town or development — future population, average daily, maximum daily and peak hourly demand, storage volume and the matching wastewater flow with Harmon’s peaking factor.

Convert a rectangular HVAC duct to its equivalent round diameter with the Huebscher (ASHRAE) formula — hydraulic diameter, aspect ratio, air velocity, friction loss rate and the nearest standard round size.

How much artificial grass to buy: strips from 2 m, 12 ft, 4 m or 15 ft rolls laid the cheaper way, seam length, offcut waste, infill sand bags, nails and total cost.

How many clay or concrete roof tiles you need: barrel (Spanish), Roman, flat or concrete tiles from the roof plan and pitch, with breakage allowance, roof load, battens and cost.

How many shiplap or tongue-and-groove boards for a wall or ceiling: net area after doors and windows, exposed board width, board length, waste, nails and cost.

How many cement backer board sheets for a shower, wall or floor: 3×5, 4×8 or 0.90×1.20 sheets with waste, backer-board screws, alkali-resistant mesh tape and thinset bags.

Countertop area for granite, quartz or laminate: straight or L-shaped runs, island and backsplash, finished edge length, number of slabs and installed cost.

Size a solar water heater for your home: daily hot water by people, recommended tank in litres or gallons, number of evacuated tubes or flat-plate area, energy and LP gas saved per year.

Size a seepage pit (soak pit) for septic tank effluent: daily wastewater, percolation test rate, required sidewall absorption area, effective depth for your pit diameter and number of pits.

How many adobe bricks for a wall: common adobe sizes with mud-mortar joints, adobes per m² or sq ft, mud mortar volume, wall thickness and total weight.

How much carpet or runner for stairs: tread, riser and nosing per step, total strip length, wall-to-wall carpet area or runner length, padding, stair rods and cost.

Handrail length for a staircase from the number of risers, riser height and tread depth: sloped length, code extensions, stair angle, stock length, brackets and handrail height.

How much landscape edging for a garden bed: edge length of a rectangle, circle or measured border, number of strips, rolls, bricks or blocks with overlap, stakes and cost.

Size natural gas or propane piping with the IFGC low-pressure equation: connected load in kW or BTU/h, longest run, pressure drop, Schedule 40 steel or copper, minimum diameter and capacity table.

How much pool paint you need: floor and wall area of a rectangular, round or oval pool from its depths, epoxy, rubber or acrylic coverage per coat, number of coats, cans and cost.

How much stone for a stone wall: mortared rubble masonry or dry stone wall from length, height and thickness, tonnes of stone, loose volume to order, mortar, cement and sand.

What size sauna heater (kW) do you need: room volume plus 1.2 m³ for every m² of glass or uninsulated wall, log-wall factor, recommended standard heater and current draw.

Board and batten wall calculator: number of vertical and horizontal battens for an accent wall or grid, or boards and battens for exterior siding, with spacing, stock lengths, nails and cost.

Waffle slab (ribbed or two-way joist slab) quantities: concrete volume, number of void formers or pans, equivalent thickness, self-weight, topping mesh and an ACI 318 rib and topping check.

Shower floor slope and mortar bed (dry pack) calculator: ¼″ per foot (2%) to the drain, thickness at the walls for a center or linear drain, mortar volume, bags and cement.