Calculating galvanized steel coil weight accurately is essential for logistics planning, container loading optimization, and cost estimation. This article provides the weight formulas, a quick-reference thickness-to-weight chart, and practical guidance for importers and fabricators working with GI/HDG steel coil.
The theoretical weight of a steel coil is calculated from its dimensions and material density:
Weight (kg) = Width (m) × Thickness (mm) × Length (m) × 7.85
Where 7.85 is the standard density of carbon steel in kg/dm³ (or metric tons per m³ per mm of thickness). For galvanized steel, the zinc coating adds approximately 0.5–2% to the calculated weight depending on coating mass:
GI Coil Weight (kg) = Base Steel Weight × (1 + zinc coating factor)
Zinc coating contribution factors:
For most logistics calculations, the base steel calculation is sufficient — the zinc coating weight is small enough that it rarely changes container loading decisions.
When you know the coil's outer diameter (OD), inner diameter (ID), and width, use this formula:
Length (m) = π × (OD² − ID²) / (4 × Thickness × 1,000)
Then multiply by width, thickness, and 7.85 as above.
Example: A coil with OD 1,200 mm, ID 508 mm, width 1,250 mm, and thickness 0.5 mm:
Standard galvanized steel coil — weight per meter of length at common widths and gauges:
| Thickness (mm) | Gauge (approx.) | Weight kg/m at 1,000mm | Weight kg/m at 1,219mm | Weight kg/m at 1,250mm | |---|---|---|---|---| | 0.20 | 32 ga | 1.57 | 1.91 | 1.96 | | 0.30 | 30 ga | 2.36 | 2.87 | 2.94 | | 0.40 | 28 ga | 3.14 | 3.83 | 3.93 | | 0.50 | 26 ga | 3.93 | 4.78 | 4.91 | | 0.60 | 24 ga | 4.71 | 5.74 | 5.89 | | 0.80 | 22 ga | 6.28 | 7.65 | 7.85 | | 1.00 | 20 ga | 7.85 | 9.57 | 9.81 | | 1.20 | 18 ga | 9.42 | 11.48 | 11.78 | | 1.50 | 16 ga | 11.78 | 14.35 | 14.72 | | 2.00 | 14 ga | 15.70 | 19.14 | 19.63 | | 2.50 | 12 ga | 19.63 | 23.92 | 24.53 | | 3.00 | 11 ga | 23.55 | 28.70 | 29.44 |
Multiply kg/m by length in meters for total coil weight. For example, 1,500 meters of 0.50 mm × 1,219 mm yields: 1,500 × 4.78 ≈ 7,170 kg.
A standard 20-foot GP container can typically hold 25–28 metric tons of steel coil, and a 40-foot GP container holds 26–28 metric tons (limited by payload, not volume). Coils are loaded eye-to-sky on wooden cradles or steel coil racks.
A common loading configuration for 1,219 mm wide coils in a 20-foot container accommodates 4–6 coils depending on OD. Buyers should work with their supplier to optimize OD and weight per coil for maximum container utilization.
For cut-to-length galvanized sheets, use:
Sheet Weight (kg) = Width (m) × Length (m) × Thickness (mm) × 7.85
Common sheet sizes and weights (Z180, calculated on base steel):
| Sheet Size (mm) | 0.40 mm | 0.50 mm | 0.60 mm | 0.80 mm | 1.00 mm | |---|---|---|---|---|---| | 1,219 × 2,438 | 9.3 | 11.7 | 14.0 | 18.6 | 23.3 | | 1,250 × 2,500 | 9.8 | 12.3 | 14.7 | 19.6 | 24.5 | | 1,500 × 3,000 | 14.1 | 17.7 | 21.2 | 28.3 | 35.3 |
Weights shown in kg per sheet. Values are approximate; actual weight varies slightly with coating mass and dimensional tolerance.
Always confirm with your supplier whether quoted coil weight is actual or theoretical. Actual weight (weighed on a calibrated scale) is the basis for ocean freight and customs declarations. Theoretical weight is an estimate used for preliminary logistics planning.
Coil weight tolerance is typically ±3% of the ordered weight. When precise weight specifications are critical (e.g., for automated roll-forming lines with maximum coil weight limits), specify the acceptable weight range in the purchase order and request weight confirmation before shipment.
Jinan Zunkai Materials provides theoretical weight calculations with every quotation and confirms actual shipping weights on the commercial invoice and packing list. Our logistics team can advise on container loading configurations to optimize freight costs for your order volume.
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