A bar is a cylinder: weight = (π d²/4) × L × 7850 kg/m³. With d in millimetres and L in metres, the constants collapse to d²/162.2 kg per metre — the number every bar bender uses.
A 12 mm bar therefore weighs 144/162 = 0.889 kg/m; a 16 mm bar 1.58 kg/m; a 20 mm bar 2.47 kg/m. Steel is billed by weight, so the schedule is the bill.
8 mm
0.395 kg/m
10 mm
0.617 kg/m
12 mm
0.889 kg/m
16 mm
1.580 kg/m
20 mm
2.470 kg/m
25 mm
3.858 kg/m
Remember on site
- Unit weight (kg/m) = d² / 162.2.
- Steel is measured by weight from the BBS (IS 1200 Part 25).
- Round ordering up to standard 12 m lengths and plan cuts to minimise offcuts.
Check yourself
Unit weight of a 12 mm bar?
Steel on site is ordered and billed by…
The standard formula for unit weight of a steel reinforcement bar in kg per metre is:
The value 162 used in the d²/162 formula comes from:
The unit weight of an 8 mm diameter bar, using d²/162, is approximately:
The unit weight of a 10 mm diameter bar is approximately:
The unit weight of a 12 mm diameter bar is approximately:
The unit weight of a 16 mm diameter bar is approximately:
The unit weight of a 20 mm diameter bar is approximately:
The unit weight of a 25 mm diameter bar is approximately:
A 12 mm bar cut to a 12 m length weighs approximately:
A BBS schedule shows a total steel requirement of 48,500 kg for a floor; expressed in tonnes with 3 percent wastage added, the quantity to order is approximately: