Total steel weight106.54 kg
In tonnes0.107 t
Weight per meter (12 mm)0.888 kg/m
Weight of one bar10.65 kg
Total length120 m
12 m bars per tonne93.9
Uses steel density 7,850 kg/m³: weight per meter = π/4 × D² × 7,850 ÷ 10⁶. The site formula D²/162 gives 0.889 kg/m for 12 mm, within 0.2% of the exact value. Add lap lengths and wastage (typically 3–5%) before ordering.
| Diameter | kg per meter | kg per 12 m bar |
|---|
| 6 mm | 0.222 | 2.66 |
| 8 mm | 0.395 | 4.74 |
| 10 mm | 0.617 | 7.4 |
| 12 mm | 0.888 | 10.65 |
| 16 mm | 1.578 | 18.94 |
| 20 mm | 2.466 | 29.59 |
| 25 mm | 3.853 | 46.24 |
| 28 mm | 4.834 | 58 |
| 32 mm | 6.313 | 75.76 |
| 36 mm | 7.99 | 95.88 |
| 40 mm | 9.865 | 118.38 |
Where D²/162 comes from
A round bar of diameter D mm has a cross-section of π/4 × D² mm². One meter of it is π/4 × D² × 10⁻⁶ m³, and at a steel density of 7,850 kg/m³ that weighs D² × 0.006165 kg — which is D² ÷ 162.2. Site engineers round this to D²/162, so a 12 mm bar weighs 144 ÷ 162 ≈ 0.889 kg per meter.
Worked example
Ten 16 mm bars, each 12 m long: 16² ÷ 162 = 1.58 kg/m, so one bar weighs about 18.96 kg and ten bars weigh about 189.6 kg. Steel is usually bought by the tonne, so that is about 0.19 t.
Nominal and actual weight
IS 1786 allows a small tolerance on the actual mass per meter of TMT bars, so a weighbridge reading can differ slightly from the calculated weight. Lap lengths, bends and cutting wastage (typically 3–5%) should be added to the quantity from the drawings before you order.
Frequently asked questions
What is the weight of a 12 mm bar per meter?
About 0.888 kg per meter, or 10.65 kg for a standard 12 m bar.
What is the formula for steel bar weight?
Weight in kg per meter = D² ÷ 162, where D is the diameter in mm. It comes from steel density 7,850 kg/m³.
How many 12 mm bars are in one tonne?
About 94 bars of 12 m length (1,000 ÷ 10.65 kg).
What is the weight of 8 mm, 10 mm and 16 mm bars?
About 0.395, 0.617 and 1.578 kg per meter respectively.