How to use the TMT steel weight calculator
- Select the bar diameter (6 mm to 40 mm) or choose “Other size”.
- Enter the length of each bar. Standard TMT bars are 12 m (about 40 ft).
- Enter the number of bars, and optionally your rate per kg for the cost.
- Use the IS 1786 option for exact nominal mass, or D² ÷ 162 if you want to match a site calculation.
Steel bar weight formula
Weight (kg/m) = π/4 × D² × 7,850 ÷ 1,000,000 = D² ÷ 162.2 Weight of one bar = kg/m × length (m) Total weight = weight of one bar × number of bars
D is the bar diameter in millimetres and 7,850 kg/m³ is the density of steel. The exact constant is 162.2; site engineers usually round it to 162.
Worked example
100 bars of 16 mm TMT, each 12 m long, at ₹65 per kg:
- kg/m = 16² ÷ 162.2 = 256 ÷ 162.2 = 1.578 kg/m
- One bar = 1.578 × 12 = 18.94 kg
- 100 bars = 1,894 kg (1.894 tonnes)
- Cost = 1,894 × 65 = ₹1,23,110
TMT bar weight chart
| Diameter | kg per metre | kg per 12 m bar | Bars per tonne |
|---|---|---|---|
| 6 mm | 0.222 | 2.66 | 375 |
| 8 mm | 0.395 | 4.74 | 211 |
| 10 mm | 0.617 | 7.40 | 135 |
| 12 mm | 0.888 | 10.65 | 94 |
| 16 mm | 1.578 | 18.94 | 53 |
| 20 mm | 2.466 | 29.59 | 34 |
| 25 mm | 3.853 | 46.24 | 22 |
| 28 mm | 4.834 | 58.00 | 17 |
| 32 mm | 6.313 | 75.76 | 13 |
| 36 mm | 7.990 | 95.88 | 10 |
| 40 mm | 9.865 | 118.38 | 8 |
Bars per tonne are rounded to whole bars. The kg/m values match the nominal masses in IS 1786.
How much steel does a house need?
A rough thumb rule used in India is 3.5–4.5 kg of steel per square foot of built-up area for a typical RCC frame house, but this varies widely with the number of floors, spans, soil and seismic zone. Always order from the bar bending schedule your structural engineer prepares, and use this calculator to check the weight of each bar size.
Tips for buying and checking TMT steel
- Weigh a sample. Cut a 1 m piece and weigh it. Compare with the chart; within the rolling tolerance is acceptable.
- Check the grade: Fe 500D is the most common grade for houses in India; Fe 550D for larger structures. The “D” means higher ductility.
- Lap lengths and bends add steel. Bar bending schedules add laps (often 40–50 × D) and hooks, so the steel you order is usually 3–8% more than the straight lengths in the drawing.
- Store bars off the ground and covered to avoid rust before use.
- Compare price per kg, not per bar — bars of the same size from different makers can differ slightly in weight.