Steel Weight Calculator
Calculate the weight of steel bars, pipes, plates, flats and angles from dimensions using the standard 7850 kg/m³ density and the D²/162 rebar rule.
Inputs
Formula
- W = ρ × A × L, ρ = 7850 kg/m³
- Round bar: W (kg/m) = D² / 162.28 with D in mm
- Pipe: A = π/4 × (D² − (D − 2t)²)
- Plate / flat: A = width × thickness
All steel weight rules reduce to mass = density × cross-sectional area × length. For round bars the constant folds together: ρ·π/4 in consistent units gives 1/162.28, so a 12 mm bar weighs 144/162.28 = 0.888 kg per metre — the number used on every bar bending schedule. Structural steel to IS 2062 / EN 10025 is taken at 7850 kg/m³.
Step-by-step calculation
Cross-section
π/4 × D²
113.1 mm²
Unit weight
ρ × A = 7850 × A / 10⁶
0.8878 kg/m
Per piece
kg/m × L
10.654 kg
Total
per piece × quantity
10.65 kg
Worked example
- 40 rebars of 12 mm diameter, 12 m long.
- Unit weight = 12² / 162.28 = 0.888 kg/m.
- Weight = 0.888 × 12 × 40 = 426.2 kg ≈ 0.43 tonne.
Assumptions
- Density 7850 kg/m³ (mild and TMT steel). Stainless is ~7900–8000 kg/m³.
- Nominal dimensions are used; rolling tolerance to IS 1786 is ±3% per bar and ±2% per lot.
Tips
- Add 3–5% wastage for cutting, laps and bends when ordering.
- Standard TMT bar lengths are 12 m; ordering in bar counts avoids off-cut waste.
Standards & references
- IS 1786 (HSD bars)
- IS 2062 (structural steel)
- IS 2502 (bar bending schedules)
Frequently asked questions
Where does the D²/162 formula come from?
Weight per metre = ρ × πD²/4. With ρ = 7850 kg/m³ and D in millimetres, 7850 × π / 4 / 1 000 000 = 1/162.28, so W = D²/162.28 kg per metre.
How many 12 mm bars are in one tonne?
A 12 m bar of 12 mm weighs 10.66 kg, so a tonne contains about 94 bars.
Does the calculator handle TMT and mild steel differently?
No — both have essentially the same density of 7850 kg/m³, so the weight is identical. Only the yield strength differs.
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