How much does #4 rebar weigh?

0.668 lb per foot (ASTM A615), so a 20 ft bar weighs 13.36 lb. In metric, 0.994 kg per metre.

How much does #7 rebar weigh?

2.044 lb per foot under ASTM A615 — a 20 ft bar weighs 40.9 lb.

What is the weight of 12 mm rebar per metre?

0.888 kg/m under IS 1786:2008, so a standard 12 m bar weighs 10.66 kg. The quick formula d² ÷ 162 gives 0.889.

How do I calculate rebar weight?

Mass per length for the bar size × length × number of bars. Ten 6 m bars of 16 mm (1.579 kg/m) weigh 1.579 × 6 × 10 = 94.7 kg.

How do I work out how much rebar a slab needs?

Count the bars each way. Bars running the length number (width ÷ spacing) + 1; bars running the width, (length ÷ spacing) + 1. A 6 × 4 m slab at 200 mm centres has 21 bars 6 m long and 31 bars 4 m long — 250 m in all, 222 kg in 12 mm bar. The spacing and size come from the design.

Where does the d² ÷ 162 rule come from?

It is a metric bar's cross-section times the density of steel: π ÷ 4 × d² mm² × 7,850 kg/m³ works out to d² ÷ 162.2 kg per metre. For 16 mm bar, 256 ÷ 162 = 1.58 kg/m, matching IS 1786's 1.579.

How many bars are in a tonne of 12 mm rebar?

A 12 m bar of 12 mm weighs 0.888 × 12 = 10.66 kg, so a tonne is about 94 bars: 1,000 ÷ 10.66 = 93.8.

Rebar Weight Calculator: kg/m and lb/ft by Bar Size

Rebar weight by bar size, length and count — metric 8–25 mm or US #3–#8 bars, in kg or lb.

Inputs

Rebar size

Length per bar(m)

0.1 m20 m

Number of bars

110,000

Units

Include CalculateEveryday mark

Total rebar weight

106.56 kg

Working: 0.888 kg/m × 6 m × 20 bars = 106.56 kg
Per bar: 5.33 kg
Weight per metre: 0.888 kg/m
Diameter: 12 mm
Bars: 20

Nominal masses per IS 1786:2008 — rolling tolerances mean delivered weight may differ slightly.
Coated or stainless grades weigh essentially the same for ordering.

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What each Rebar Weight input means

Rebar size: The bar size: metric 8–25 mm (IS 1786 masses) or US bar numbers #3–#8 (ASTM A615 weights). A US bar's number is its diameter in eighths of an inch, so #5 is ⅝ inch.
Length per bar: The length of each bar, in metres or feet, including any lap where bars overlap.
Number of bars: How many bars of that length and size. For mixed lengths, run the page once for each length and add the weights.
Units: Metric gives kg per metre and kilograms; US units give pounds per foot and pounds.

Rebar Weight formula

weight = mass per length (by bar size) × length × number of bars · 1 lb/ft = 1.488 kg/m

W = m_{\ell} \times L \times n

Each bar size has a nominal mass per unit length set by its standard — kilograms per metre under India's IS 1786, pounds per foot under ASTM A615 for US bar numbers. Both come from the bar's nominal circular cross-section and the density of steel (7,850 kg/m³), which for metric bars works out to d² ÷ 162 kg/m with d in millimetres: 12² ÷ 162 = 0.889, listed as 0.888. A US bar's number is its diameter in eighths of an inch, so #4 is ½ inch and weighs 0.668 lb/ft. Multiply the mass per length by each bar's length and the number of bars. US bar sizes can be worked in kilograms too: 1 lb/ft is 1.488 kg/m.

Rebar Weight worked example

Twenty 6 m lengths of 12 mm bar: IS 1786 gives 0.888 kg per metre, so 0.888 × 6 × 20 = 106.56 kg. The nearest US size is #4 (½ inch): ASTM A615 lists 0.668 lb per foot, so a 20 ft bar weighs 13.36 lb and twenty of them 267.2 lb.

More Rebar Weight examples

Thirty 20 ft bars of #4: 0.668 lb/ft × 20 ft = 13.36 lb a bar, and 30 bars weigh 400.8 lb.

Ten 12 m bars of 16 mm: IS 1786 lists 1.579 kg/m, so 18.95 kg a bar and 189.48 kg for the bundle.

Where the Rebar Weight calculator can give the wrong answer

Nominal weights. Rolling tolerances allow delivered bars to be a few per cent off and still in specification.
Lap splices add length: where bars overlap, count the overlap in the length.
Grade (40, 60, 75…) does not change the weight of a US bar; diameter does.
Mesh is sold by the sheet with its own weight per sheet; it is not a bar-length calculation.

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Rebar Weight reference table

Nominal rebar weights by size
Bar	Diameter	Weight	In the other unit
8 mm	8 mm	0.395 kg/m	0.265 lb/ft
10 mm	10 mm	0.617 kg/m	0.415 lb/ft
12 mm	12 mm	0.888 kg/m	0.597 lb/ft
16 mm	16 mm	1.579 kg/m	1.061 lb/ft
20 mm	20 mm	2.466 kg/m	1.657 lb/ft
25 mm	25 mm	3.854 kg/m	2.590 lb/ft
#3	⅜ in	0.376 lb/ft	0.560 kg/m
#4	½ in	0.668 lb/ft	0.994 kg/m
#5	⅝ in	1.043 lb/ft	1.552 kg/m
#6	¾ in	1.502 lb/ft	2.235 kg/m
#7	⅞ in	2.044 lb/ft	3.042 kg/m
#8	1 in	2.670 lb/ft	3.973 kg/m

Source: IS 1786:2008 nominal masses (metric bars) and ASTM A615 nominal weights (US bar numbers); converted at 1 lb/ft = 1.48816 kg/m

Rebar Weight FAQ

: 0.668 lb per foot (ASTM A615), so a 20 ft bar weighs 13.36 lb. In metric, 0.994 kg per metre.
: 2.044 lb per foot under ASTM A615 — a 20 ft bar weighs 40.9 lb.
: 0.888 kg/m under IS 1786:2008, so a standard 12 m bar weighs 10.66 kg. The quick formula d² ÷ 162 gives 0.889.
: Mass per length for the bar size × length × number of bars. Ten 6 m bars of 16 mm (1.579 kg/m) weigh 1.579 × 6 × 10 = 94.7 kg.
: Count the bars each way. Bars running the length number (width ÷ spacing) + 1; bars running the width, (length ÷ spacing) + 1. A 6 × 4 m slab at 200 mm centres has 21 bars 6 m long and 31 bars 4 m long — 250 m in all, 222 kg in 12 mm bar. The spacing and size come from the design.
: It is a metric bar's cross-section times the density of steel: π ÷ 4 × d² mm² × 7,850 kg/m³ works out to d² ÷ 162.2 kg per metre. For 16 mm bar, 256 ÷ 162 = 1.58 kg/m, matching IS 1786's 1.579.
: A 12 m bar of 12 mm weighs 0.888 × 12 = 10.66 kg, so a tonne is about 94 bars: 1,000 ÷ 10.66 = 93.8.