Calculator
TMT Bar Weight Calculator
Calculate the weight of any TMT steel bar using the D²÷162 formula. Enter diameter, length, and quantity — get kg/metre, kg/bar, and total weight instantly.
Weight / metre
0.888 kg/m
12² ÷ 162
Weight / bar
10.66 kg
0.888 × 12m
Total weight
10.7 kg
1 bar
Formula: Weight (kg/m) = D² ÷ 162, where D = diameter in mm. Per IS 1786.
The D²÷162 formula explained
Weight (kg/m) = D² ÷ 162
where D = bar diameter in mm
This formula is the standard method for calculating the theoretical unit weight of deformed steel bars (TMT bars) as specified in IS 1786. The constant 162 is derived from the density of steel (7,850 kg/m³) combined with the geometric conversion factor (π ÷ 4 × 10⁻⁶ for mm² to m²): 4 ÷ (π × 7850 × 10⁻⁶) ≈ 162.
The result is the nominal weight per metre. Actual bars may vary ±2% from nominal weight, within IS 1786 tolerances. For procurement, always add 3–5% to account for cutting, bending, and lapping losses.
TMT bar weight reference — all standard diameters
| Diameter | kg / metre | kg / 12m bar | |
|---|---|---|---|
| 8mm | 0.395 | 4.74 | |
| 10mm | 0.617 | 7.40 | |
| 12mm | 0.888 | 10.66 | |
| 16mm | 1.578 | 18.94 | |
| 20mm | 2.466 | 29.59 | |
| 25mm | 3.853 | 46.24 | |
| 32mm | 6.313 | 75.76 | |
| Theoretical weights per D²÷162 formula. Standard bar length = 12m. | |||
Worked examples
How much does a 100-bar bundle of 12mm TMT weigh?
- 1.Weight per metre: 12² ÷ 162 = 0.888 kg/m
- 2.Weight per 12m bar: 0.888 × 12 = 10.66 kg
- 3.Total for 100 bars: 10.66 × 100 = 1,066 kg = 1.066 tonnes
I need 2 tonnes of 16mm bars — how many bars is that?
- 1.Weight per 12m bar: 16² ÷ 162 × 12 = 2.56 × 12 = 18.94 kg
- 2.Bars per tonne: 1000 ÷ 18.94 = 52.8 bars
- 3.2 tonnes = 2 × 52.8 = 105.6 → order 106 bars (rounding up)
Frequently asked questions
How much does a 12mm TMT bar weigh per metre?
A 12mm TMT bar weighs 0.888 kg per metre. Using the D²÷162 formula: 12² ÷ 162 = 144 ÷ 162 = 0.888 kg/m. A standard 12m bar weighs approximately 10.66 kg.
What is the D squared divided by 162 formula?
The D²÷162 formula calculates the theoretical weight per metre of a mild steel or TMT bar. D is the bar diameter in millimetres. The constant 162 is derived from the density of steel (7850 kg/m³) and π/4. The result is in kg/m. This formula is accurate for IS 1786 TMT bars.
How many TMT bars are in one tonne?
It depends on diameter and length. For 12mm bars (standard 12m length): one bar weighs ~10.66 kg, so 1 tonne = 1000 ÷ 10.66 ≈ 94 bars. For 16mm bars (~18.94 kg): 1 tonne ≈ 53 bars. Use this calculator to get the exact count for your size.
What is the standard length of a TMT bar in India?
Standard TMT bars are supplied in 12-metre lengths (also called STS — Standard Trading Sizes). Some manufacturers also supply 9m and 6m bars for smaller projects. The weight calculation applies regardless of length: multiply kg/m by the actual length.
How accurate is the theoretical weight calculation?
The D²÷162 formula gives the theoretical (nominal) weight. Actual bars can vary ±2% from the nominal weight under IS 1786 tolerances. For procurement, add 3–5% wastage to account for cutting, bending, and lapping.
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