Construction
TMT Steel Bar Weight per Metre: The D²/162 Formula and Chart
The D²/162 formula and where it comes from, a TMT weight chart from 6 to 32 mm, and thumb rules for steel in slabs, beams and columns.
By Team Vind · Updated · 4 min read
TMT bars are sold by weight, but drawings and bar-bending schedules give lengths and diameters. To check a bill, estimate an order or compare quotes, you need one formula: the weight per metre of a bar.
The D²/162 formula
Weight (kg per metre) = D² ÷ 162 · D = diameter in mm
A 12 mm bar weighs 12 × 12 ÷ 162 = 0.889 kg per metre. A full 12 m bar is 10.67 kg.
Where 162 comes from
Steel weighs 7,850 kg per cubic metre. A bar 1 metre long has a volume of π × D² ÷ 4 square millimetres × 1 metre. Multiply by the density and convert units, and you get D² × 0.006165, which is the same as D² ÷ 162.2.
Weight chart for TMT bars
| Diameter | kg per metre | kg per 12 m bar | Bars per tonne (approx.) |
|---|---|---|---|
| 6 mm | 0.222 | 2.67 | 375 |
| 8 mm | 0.395 | 4.74 | 211 |
| 10 mm | 0.617 | 7.41 | 135 |
| 12 mm | 0.889 | 10.67 | 94 |
| 16 mm | 1.58 | 18.96 | 53 |
| 20 mm | 2.469 | 29.63 | 34 |
| 25 mm | 3.858 | 46.3 | 22 |
| 32 mm | 6.321 | 75.85 | 13 |
Try it: Steel Weight Calculator
Steel Weight
Working
- Weight per metre = 12² ÷ 162 = 0.889 kg
- Total = 0.889 × 12 m × 10 = 106.67 kg
Worked example
Your bar schedule calls for 40 bars of 12 mm, each 12 m. Weight = 40 × 12 × 0.889 = 426.7 kg, or about 0.43 tonnes. At ₹65 per kg, that's roughly ₹27,733.
Steel per cubic metre of concrete (thumb rules)
For a first estimate before the structural drawings are ready, engineers use the share of steel in each element:
| Element | Steel (% of concrete) | kg per m³ of concrete |
|---|---|---|
| Footing | 0.8% | 62.8 |
| Slab | 1% | 78.5 |
| Beam | 2% | 157 |
| Column | 2.5% | 196.3 |
For a whole house, a common budget figure is 3 to 4.5 kg of steel per square foot of built-up area. See the full breakdown in materials for a 1,000 sq ft house.
Frequently asked questions
What is the weight of a 10 mm steel bar?
0.617 kg per metre, so a 12 m bar weighs about 7.41 kg.
How many 12 mm bars are in a tonne?
About 94 bars of 12 m each.
Why is it D² divided by 162?
Steel's density is 7,850 kg/m³. The weight of a 1 m bar works out to D² × 0.006165 kg, which equals D² ÷ 162.2.
What is the standard length of a TMT bar?
12 metres in India. Shorter lengths are cut on site.
Sources
- IS 1786: High strength deformed steel bars for concrete reinforcement (Bureau of Indian Standards)
- IS 456: Plain and reinforced concrete, code of practice (reinforcement limits)
Last reviewed: 10 October 2026