Rebar Size & Weight Chart - Imperial and Metric

Imperial bar sizes (US)

The bar number is the diameter in eighths of an inch: a #4 bar is 4⁄8 inch, or 1⁄2 inch. Weights below are the standard nominal values for deformed steel bars (ASTM A615 / A706).

Bar	Nominal dia. (in)	Weight (lb/ft)	20 ft bar (lb)	40 ft bar (lb)	Area (in²)	40 ft bars / ton
#3	0.375	0.376	7.5	15.0	0.11	133
#4	0.500	0.668	13.4	26.7	0.20	74
#5	0.625	1.043	20.9	41.7	0.31	47
#6	0.750	1.502	30.0	60.1	0.44	33
#7	0.875	2.044	40.9	81.8	0.60	24
#8	1.000	2.670	53.4	106.8	0.79	18
#9	1.128	3.400	68.0	136.0	1.00	14
#10	1.270	4.303	86.1	172.1	1.27	11
#11	1.410	5.313	106.3	212.5	1.56	9
#14	1.693	7.650	153.0	306.0	2.25	6
#18	2.257	13.600	272.0	544.0	4.00	3

Swipe the table sideways for more columns →

Bars per ton are rounded down, and assume 40 ft stock. Stock lengths vary by supplier and region — check what your yard actually stocks before ordering.

Metric bar sizes

Metric bar sizes are given directly as the nominal diameter in millimetres. Weights use the standard density of steel, 7,850 kg/m³.

Size (mm)	Weight (kg/m)	12 m bar (kg)	Area (mm²)	12 m bars / tonne
10	0.617	7.4	79	135
12	0.888	10.7	113	93
16	1.578	18.9	201	52
20	2.466	29.6	314	33
25	3.853	46.2	491	21
28	4.834	58.0	616	17
32	6.313	75.8	804	13
40	9.865	118.4	1,257	8

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12 m bars per tonne are rounded down. Common stock lengths outside the US are 6 m and 12 m.

Imperial and metric — closest common pairings

Metric and imperial bar sizes do not convert exactly. These are the pairings most often treated as equivalents in practice:

#3 ≈ 10 mm
#4 ≈ 13 mm (12 mm is the nearest common metric size)
#5 ≈ 16 mm
#6 ≈ 20 mm
#8 ≈ 25 mm
#10 ≈ 32 mm

They are close, but not identical — the areas differ by a few percent, which matters if you are substituting one for the other on a designed job. Substitute only with your engineer's approval.

How to use this with the calculator

Pick the bar size and spacing, enter your slab or wall dimensions, and the rebar calculator returns the bar count, total length, lap allowance, total weight and a cost estimate. The weight figures it uses are derived the same way as the tables above — from the nominal bar diameter and the density of steel — so they agree to within a fraction of a percent.

If you already know your total length and just want a weight, take the weight per foot from the table above and multiply.

Open the Rebar Calculator → Free, no login, runs in your browser

Notes on accuracy

Nominal, not measured. The diameters and weights above are nominal values from the relevant standards. Actual bars have rolling tolerances, and deformed bars are specified by nominal size rather than by a measured diameter. Coated bars (epoxy, galvanised) add weight on top. Use these figures for estimating, and the mill certificate or your supplier's data for anything critical.

Rebar calculator — bar counts, lengths, weight and cost from your dimensions
About this site — how the numbers are worked out, and what the tool does not do

Table last reviewed: 17 September 2026

Imperial bar sizes (US)

Metric bar sizes

Imperial and metric — closest common pairings

How to use this with the calculator

Notes on accuracy

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