Rebar (TMT Steel) Weight Calculator
Steel weight from bar size, length and count — IS 1786, D²/162 and US bar sizes.
Bars
Mass, stock length and price
By bar size
| Size | kg/m | D²/162 | Length (m) | Weight (kg) | Stock bars | Bars per tonne |
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About the Rebar (TMT Steel) Weight Calculator
Find the weight of reinforcing steel from the bar size, the length of each bar and how many there are. Indian TMT sizes use the nominal masses in IS 1786 Table 1 — 8 mm is 0.395 kg/m, 12 mm 0.888 kg/m and 16 mm 1.58 kg/m — and you can switch to the site formula D²/162 to compare. US bars #3 to #18 use the ASTM A615 nominal weights in lb/ft.
Add as many rows as your bar schedule has. You get the total weight in kg, tonnes and lb, the weight per size, bars per tonne and the number of stock bars (12 m by default) to buy — planned so that offcuts are counted, not just the total length divided by 12 — and the cost at your price per kg or tonne.
How to use it
- Choose the bar size — an IS 1786 size such as 12 mm, a US size such as #4, or a custom diameter.
- Enter the length of each bar as cut (include hooks, bends and laps) and the number of bars. Use Add bar size for each diameter or length in your schedule.
- Set the stock bar length your supplier sells (12 m by default) and, if you like, a price per kg, tonne, lb or US ton.
- Read the total weight, the stock bars to buy and the table by size; copy the result or download it as CSV.
Examples
120 m × 0.888 kg/m = 106.56 kg · 10 stock bars · 93.8 bars of 12 m per tonne
60 m × 0.395 kg/m = 23.7 kg · cut from 5 bars of 12 m (10 pieces per bar)
70 m × 1.58 kg/m = 110.6 kg · needs 10 stock bars of 12 m (one piece per bar, 50 m of offcuts) — not the 6 that 70 ÷ 12 suggests
200 ft × 0.668 lb/ft = 133.6 lb (60.6 kg)
Mass per metre: IS 1786 table and D²/162
IS 1786 works out nominal mass from a steel density of 0.00785 kg per mm² of cross-section per metre (7,850 kg/m³), so a bar of diameter D mm weighs π/4 × D² × 0.00785 = D²/162.2 kg/m. On site this is rounded to D²/162: 12² ÷ 162 = 0.889 kg/m.
IS 1786:2008 Table 1 (nominal mass, kg/m): 6 mm 0.222 · 8 mm 0.395 · 10 mm 0.617 · 12 mm 0.888 · 16 mm 1.58 · 20 mm 2.47 · 25 mm 3.85 · 28 mm 4.83 · 32 mm 6.31 · 36 mm 7.99 · 40 mm 9.86 — and 45 mm 12.49 and 50 mm 15.42, added by Amendment 1 (2012).
The batch tolerance on mass (Table 2) is ±7% up to 10 mm, ±5% over 10 mm up to 16 mm and ±3% above 16 mm, so the weighbridge weight of a delivery can differ from the nominal weight.
US bar sizes (ASTM A615)
Nominal weights in lb/ft: #3 0.376 · #4 0.668 · #5 1.043 · #6 1.502 · #7 2.044 · #8 2.670 · #9 3.400 · #10 4.303 · #11 5.313 · #14 7.65 · #18 13.60. Up to #8 the bar number is the diameter in eighths of an inch (#4 = ½ in, 12.7 mm); the metric names #10 to #57 are the same bars in millimetres. To convert, 1 lb/ft = 1.48816 kg/m, so #4 is 0.994 kg/m. The 1979 edition of A615 that we checked (§13.1) lets a bar weigh up to 6% less than its nominal weight.
Stock bars and offcuts
Steel is bought in stock lengths and cut. Dividing the total length by 12 m only works when the pieces fit neatly; ten 7 m pieces need ten 12 m bars, because each bar leaves a 5 m offcut. The calculator places the longest pieces first, each into the first stock bar with enough length left (first-fit decreasing), which is close to the best possible plan. It shows the offcut length and the weight of the stock bars you actually buy, which is what the cost is based on. Pieces longer than a stock bar need laps or couplers — add the lap to the piece length.
Sources
- IS 1786:2008 (with Amendment 1, 2012), High Strength Deformed Steel Bars and Wires for Concrete Reinforcement, cl. 6.1, 7.2.1, Table 1 and Table 2 — archive.org
- ASTM A615, Deformed and Plain Billet-Steel Bars for Concrete Reinforcement, Table 1 nominal weights, as published in A615-79 — archive.org
- Pound and foot conversions: NIST SP 811 Appendix B (1 lb = 0.45359237 kg, 1 ft = 0.3048 m)
Limitations
- Lengths are taken as entered: add hooks, bends and laps to each cut length yourself (a bar bending schedule does this for every shape).
- Weights are nominal. Delivered steel can be heavier or lighter within the standard's tolerance.
- The cutting plan ignores saw-cut widths and the reuse of offcuts from other sizes; treat it as a purchasing estimate.
- Reinforcement sizes, spacing and laps come from your structural engineer's drawings — this tool only weighs them.
Privacy
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Frequently asked questions
What is the weight of a 12 mm TMT bar per metre?
0.888 kg per metre (IS 1786 Table 1). By the D²/162 formula it is 144 ÷ 162 = 0.889 kg/m. A 12 m bar weighs about 10.66 kg, so a tonne is about 94 bars.
Why is steel weight D²/162?
A round bar of diameter D mm has an area of π/4 × D² mm². Steel weighs 7,850 kg/m³, which is 0.00785 kg per mm² per metre, so the mass is π/4 × 0.00785 × D² = D² ÷ 162.2 kg/m — rounded to 162 on site.
How many bars are in one tonne?
Divide 1,000 kg by the weight of one stock bar. For 12 m bars: 8 mm about 211, 10 mm about 135, 12 mm about 94, 16 mm about 53, 20 mm about 34 and 25 mm about 22.
Why does the delivered weight differ from my calculation?
Bars are made to a nominal mass with a tolerance — for a batch, IS 1786 allows ±7% for sizes up to 10 mm, ±5% over 10 mm up to 16 mm and ±3% above that. Rolling margins, rust and cut lengths also make a difference.
How much does #4 rebar weigh?
A #4 bar (½ in, 13 mm) weighs 0.668 lb per foot (ASTM A615), so a 20 ft bar weighs 13.36 lb and ten of them 133.6 lb.