Rebar Weight & Area
Gives the nominal diameter, cross-sectional area and weight per length of a reinforcing bar, and the total weight of a length of it. It covers ASTM A615 inch bars #3 to #18 [1], CSA G30.18 metric bars 10M to 55M [2], BS 4449 / EN 10080 metric bars 8 to 50 mm [3], and any other round bar by its diameter. Estimators use it for steel takeoffs and shipping weights; designers use the area to turn a required steel area into a bar count.
Where the numbers come from
For ASTM and CSA bars the diameter, area and mass are the nominal values tabulated in the standards, and the page shows them as published. The ASTM mass is listed in lb/ft and converted to kg/m. A deformed bar is not round, so its nominal diameter is that of a plain bar with the same mass per length. For BS 4449 sizes and custom bars the page computes:
A = πd²/4 m = ρA W = m·L
d is the nominal diameter, A the area, ρ = 7,850 kg/m³ the density of steel that the bar standards use, m the mass per meter, L the length and W the total weight. The weight in pounds is W × 2.20462.
Limits and common mistakes
- Enter the total length of all bars of one size, including laps, hooks and bends, not the length of the member.
- ASTM bars are often rolled with their soft-metric number, so a #5 bar may be marked 16 (No. 16). CSA 15M (16.0 mm) is a different bar.
- The weights are nominal. Mill tolerance allows each bar to be several percent light, so order by count and length, not by weight alone.
- Epoxy coating and galvanizing add a little weight that the page leaves out.
Worked example
A slab edge needs 48 #5 bars, each 20 ft long. Find the shipping weight for the delivery ticket.
- Choose Bar Size #5 [No. 16], under ASTM A615 (US).
- Set the Length unit to ft and enter 960 (48 bars × 20 ft).
- Press Solve. The Solution shows:
Nominal Diameter: 15.9 mm
Cross-Sectional Area: 200 mm²
Weight per Length: 1.55215 kg/m
Total Weight: 454.173 kg
Total Weight: 1,001.28 lb
Check: A615 lists #5 at 1.043 lb/ft, and 1.043 × 960 = 1,001.28 lb. A plain 15.9 mm steel rod weighs 7,850 × π/4 × 0.0159² = 1.559 kg/m, within 0.5 % of the bar’s nominal 1.552 kg/m.