Rebar Weight Calculator
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.
How it works
total length = bar length × number of bars (× (1 + laps%)) · weight = total length × unit weight (e.g. #4 = 0.668 lb/ft = 0.994 kg/m) · tons = pounds ÷ 2,000; tonnes = kg ÷ 1,000 · any diameter: kg/m = d² ÷ 162.2 (d in mm, steel 7,850 kg/m³) · bars in a weight = weight ÷ unit weight ÷ bar length
Reinforcing bar is sold by weight, and each size has a fixed weight per length set by its cross-section. US bar numbers are the nominal diameter in eighths of an inch, so a #4 bar is 4/8 = 1/2 in and weighs 0.668 lb per foot under ASTM A615. Canadian bars (10M, 15M…) and metric bars (8, 10, 12 mm…) are named in millimeters and weighed in kilograms per meter. Any round steel bar weighs d² ÷ 162.2 kg per meter with d in millimeters, which is π/4 × d² times the 7,850 kg/m³ density of steel. Multiply the unit weight by the total length to get the weight, and add a percentage for lap splices and offcuts if you are estimating a job. You can also work backward from a total length to the number of stock bars, or from a weight on an invoice to the number of bars it represents. Prices can be entered per pound, per ton, per bar or per foot.
Worked example
Fifty #4 bars, each 20 ft long: total length is 50 × 20 = 1,000 ft. At 0.668 lb/ft that is 668 lb, or 0.334 tons (303 kg), and one bar weighs 20 × 0.668 = 13.4 lb. A ton of #4 in 20 ft bars is 2,000 ÷ 13.36 = about 150 bars.
Sources: ASTM A615 standard rebar weights · Inch Calculator — US, Canadian and European rebar weight tables · Omni Calculator — steel bar weight from diameter and density (d² ÷ 162)
Frequently asked questions
What does the rebar size number mean?
In US bar sizes the number is the nominal diameter in eighths of an inch. A #3 bar is 3/8 in, a #4 is 1/2 in, a #5 is 5/8 in, and so on up to #18 at 2¼ in. Larger numbers mean thicker, heavier bar. Canadian and metric bars are named by their size in millimeters instead.
How heavy is #4 rebar per foot?
A #4 bar weighs about 0.668 lb per linear foot (0.994 kg/m). Common others are #3 at 0.376, #5 at 1.043, #6 at 1.502 and #8 at 2.670 lb per foot. A 20 ft #4 bar weighs 13.4 lb.
How do I find the weight of a metric or odd-size bar?
Square the diameter in millimeters and divide by 162.2 to get kilograms per meter. A 12 mm bar is 144 ÷ 162.2 = 0.888 kg/m, and a 16 mm bar is 1.578 kg/m. Choose Other diameter to use any size, in mm or inches.
How many bars are in a ton of rebar?
Divide the ton by the weight of one bar. In 20 ft lengths a ton (2,000 lb) is about 266 bars of #3, 150 of #4 or 96 of #5. Choose Total weight to turn any weight into a bar count for your bar length.
Why calculate rebar weight?
Suppliers price and ship rebar by weight, and knowing the tonnage helps you plan delivery, check an invoice and estimate the load on a truck or a floor. It also feeds into structural steel-ratio checks.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.