| OD (mm) | Weight (kg) | Strip @ 2 mm (m) | Strip @ 3 mm (m) | Coils / 25 t |
|---|---|---|---|---|
| 1000 | 4,839 | 247 | 164 | 5 |
| 1200 | 8,230 | 419 | 280 | 3 |
| 1400 | 12,237 | 624 | 416 | 2 |
| 1600 | 16,862 | 859 | 573 | 1 |
| 1800 | 22,102 | 1,126 | 751 | 1 |
| 2000 | 27,959 | 1,425 | 950 | 0 |
Carbon steel at 7,850 kg/m³. Scale linearly for other widths; use the calculator for other IDs and materials.
A coil is a hollow cylinder. Its volume is the annulus area (outer circle minus the eye) times the width; multiply by density to get mass:
Where OD and ID are the outer and inner diameters in mm, W is the coil width in mm and ρ is density in kg/m³ (7,850 for carbon steel, 8,000 for SS 304, 2,700 for aluminium).
Step 1: π/4 × (1600² − 610²) = 1,718,373 mm²
Step 2: × 1,250 × 7,850 ÷ 10⁹ = 16,862 kg
Length: 1,718,373 ÷ 2 ÷ 1,000 = 859 m of strip
Working the other way, buyers who specify a maximum coil weight for their decoiler can enter the weight and get the OD the mill must hold. Pair this with the plate and sheet calculator for cut-to-length yields, or the gauge converter when a coil is quoted in gauge.
Coil weight = π/4 × (OD² − ID²) × width × density ÷ 10⁹, with OD, ID and width in millimetres and density in kg/m³ (7,850 for carbon steel). Example: a 1,250 mm wide HR coil with OD 1,600 mm and ID 610 mm weighs π/4 × (1600² − 610²) × 1250 × 7850 ÷ 10⁹ ≈ 16,860 kg.
Strip length (m) = coil weight (kg) ÷ (width (mm) × thickness (mm) × density ÷ 10⁶). A 16,860 kg coil, 1,250 mm wide and 2 mm thick, holds 16,860 ÷ (1250 × 2 × 7850 ÷ 10⁶) ≈ 859 metres of strip. The same length follows from geometry: π/4 × (OD² − ID²) ÷ thickness.
Hot-rolled coils are most often supplied on 762 mm (30 inch) or 610 mm (24 inch) eyes; cold-rolled and galvanised coils commonly use 508 mm (20 inch) or 610 mm. Always confirm the ID with the mill test certificate, because it drives both strip length and your decoiler mandrel setting.
Divide the legal payload by coil weight. In India a standard multi-axle trailer carries about 25 tonnes, so a 16.9 t coil travels alone and two 12 t coils share a load. The calculator shows coils per 25 t load for the dimensions you enter.
Thickness and width tolerances (IS 1079, IS 513, EN 10051) allow the real section to sit a little above or below nominal, and coil wraps are not perfectly tight. Expect ±2 to 3% between theoretical and weighbridge weight; invoices follow the weighbridge, not the formula.