Pool Volume Calculator (Gallons)
Work out how many gallons or liters your pool holds — rectangular, round, oval, kidney or L-shaped, with a sloped floor — plus fill time, fill cost, pump flow and water per inch of level.
How it works
Rectangular: L × W × depth · Round: π × (D ÷ 2)² × depth · Oval: π × (L ÷ 2) × (W ÷ 2) × depth · Kidney ≈ 0.45 × L × (A + B) × depth · L-shape: sum of the two rectangles · Average depth = (shallow + deep) ÷ 2 · Gallons = cubic feet × 7.48 · Liters = m³ × 1,000 · Fill time = volume ÷ flow rate
A pool’s volume is its water surface area multiplied by its average water depth. The area formula depends on the outline: length × width for a rectangle, π × radius² for a circle, π × half-length × half-width for an oval (an ellipse), and for a kidney or oblong pool the common pool-trade approximation 0.45 × length × (wide-end width + narrow-end width). An L-shaped pool is two rectangles added together, each with its own depth. If the floor slopes, enter the shallow-end and deep-end depths and the calculator averages them, which treats the floor as an even ramp. One cubic foot holds 7.48 US gallons and one cubic meter holds 1,000 liters. From the volume the calculator also gives the fill time at your hose or truck flow rate, the cost of the water at your utility’s price, the pump flow needed to turn the water over in a set number of hours, how much water one inch (or one centimeter) of level represents — handy for evaporation and backwash losses — and the amount of 12.5% liquid chlorine or 65% calcium hypochlorite that raises free chlorine by 1 ppm.
Worked example
A 32 × 16 ft rectangular pool has a 512 sq ft surface. With a 3.5 ft shallow end and an 8 ft deep end the average depth is 5.75 ft, so it holds 512 × 5.75 = 2,944 cubic feet, or 2,944 × 7.48 ≈ 22,020 gallons (83,400 liters). At the default 5 ft average depth the same pool holds about 19,150 gallons; filling that from a 10 gal/min garden hose takes about 31 hours 55 minutes, and at $5 per 1,000 gallons the water costs about $95.75. An 8-hour turnover needs a pump moving about 40 gallons a minute.
Frequently asked questions
How many gallons is my pool?
Multiply the surface area by the average water depth to get cubic feet, then multiply by 7.48 for US gallons (or multiply cubic meters by 1,000 for liters). Pick the shape in the calculator and it applies the right area formula — including kidney and L-shaped pools.
How do I find the average depth?
Add the shallow-end and deep-end water depths and divide by two — a pool that runs from 3.5 ft to 8 ft averages 5.75 ft. Choose “Shallow & deep end” and the calculator does this for you. Measure water depth, not wall height.
How do I measure a kidney-shaped or freeform pool?
Measure the overall length and the width across each end, then use area ≈ 0.45 × length × (sum of the end widths). For a very irregular pool, split it into rectangles and circles, work out each piece and add them — the L-shaped option handles two rectangles with different depths.
How long does it take to fill a pool with a garden hose?
Divide the volume by the hose flow. A typical 5/8-inch hose gives about 9–12 gallons a minute, so a 20,000-gallon pool takes roughly 28–37 hours. Time how long your hose takes to fill a 5-gallon bucket for an exact rate, and enter it under More options.
What size pump do I need?
Divide the volume by the turnover time you want, in minutes. A 19,150-gallon pool on an 8-hour turnover needs about 19,150 ÷ 480 ≈ 40 gallons a minute of actual flow; check the pump’s flow at your system’s head (resistance), not its maximum rating.
Why do I need the volume?
Nearly every pool task depends on it: dosing chlorine and balancing chemicals, sizing a pump, filter or heater, estimating heating costs, and knowing how long the pool takes to fill or drain.
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This calculator is for educational purposes. Double-check important results before acting on them.