Rebar Weight Calculator
By Santaji GadepatilinUpdated October 27, 2026
Reinforcement steel is ordered by weight, while drawings specify lengths and diameters. The weight per metre follows from the bar diameter — D²/162 kg/m for steel. This free rebar weight calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the rebar weight calculator
Choose the bar diameter, then enter the length and number of bars. The weight per metre and total weight are calculated.
Rebar weight formula
kg/m = d² ÷ 162.2
Example
10 bars of 12 mm, each 12 m long:
- Weight per metre = 144 ÷ 162.2 = 0.888 kg/m
- Total = 0.888 × 12 × 10 = 106.5 kg
Bars per tonne
| Diameter | kg/m | Metres per tonne | 12 m bars per tonne |
|---|---|---|---|
| 8 mm | 0.395 | 2,534 | 211.2 |
| 10 mm | 0.617 | 1,622 | 135.2 |
| 12 mm | 0.888 | 1,126 | 93.9 |
| 16 mm | 1.578 | 634 | 52.8 |
| 20 mm | 2.466 | 406 | 33.8 |
| 25 mm | 3.853 | 260 | 21.6 |
| 32 mm | 6.313 | 158 | 13.2 |
Where the formula comes from
Steel density is 7,850 kg/m³. For a 1 m bar of diameter d (mm):
Weight = π × (d ÷ 2000)² × 1 × 7,850 = d² ÷ 162.2
US bar sizes
| US bar | Diameter | lb/ft |
|---|---|---|
| #3 | 3/8 in (9.5 mm) | 0.376 |
| #4 | 1/2 in (12.7 mm) | 0.668 |
| #5 | 5/8 in (15.9 mm) | 1.043 |
| #6 | 3/4 in (19.1 mm) | 1.502 |
| #8 | 1 in (25.4 mm) | 2.670 |
The number is the diameter in eighths of an inch.
Estimating steel for a slab
Typical residential RCC uses roughly 80–120 kg of steel per m³ of concrete for slabs and 150–250 kg/m³ for columns and beams. Use these only for rough budgets — the structural design gives exact quantities.
Laps and wastage
Add for lap lengths (often 40–50 × bar diameter), bends and offcuts. Allow 3–5% wastage for cutting.
Weight per metre table
| Diameter | kg/m | 12 m bar |
|---|---|---|
| 6 mm | 0.222 | 2.66 kg |
| 8 mm | 0.395 | 4.73 kg |
| 10 mm | 0.617 | 7.40 kg |
| 12 mm | 0.888 | 10.65 kg |
| 16 mm | 1.578 | 18.94 kg |
| 20 mm | 2.466 | 29.59 kg |
| 25 mm | 3.853 | 46.24 kg |
| 32 mm | 6.313 | 75.76 kg |
Frequently asked questions
What is the formula for rebar weight?
Weight (kg/m) = d² ÷ 162.2, where d is the diameter in mm. It comes from steel's density of 7,850 kg/m³.
How much does a 12 m, 12 mm bar weigh?
About 0.888 kg/m × 12 m = 10.65 kg.
Is TMT bar weight the same?
Yes — TMT and other deformed bars are rated by nominal diameter and use the same formula.
What is the weight of 12 mm rebar per metre?
0.888 kg/m.
How many 12 m bars of 10 mm make a tonne?
About 135 bars.