How to Calculate Steel Plate Weight (Formula and Examples)
Steel plate weight formula with worked examples: length × width × thickness × 7.85, kg per square metre, stainless density, cut shapes and a quick reference table.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: Steel plate weight (kg) = length (m) × width (m) × thickness (mm) × 7.85. Each millimetre of thickness weighs 7.85 kg per square metre, so a 10 mm plate weighs 78.5 kg/m². For stainless steel use about 7.9–8.0 instead of 7.85.
Plate weight matters for pricing, transport, lifting and structural loads. Fortunately, the calculation is simple.
The formula
Steel density is 7,850 kg/m³. One square metre of steel 1 mm thick has a volume of 0.001 m³, so it weighs 7.85 kg. Therefore:
Weight (kg) = L (m) × W (m) × t (mm) × 7.85
Worked examples
| Plate | Calculation | Weight |
|---|---|---|
| 1.5 × 6 m × 6 mm | 1.5 × 6 × 6 × 7.85 | 423.9 kg |
| 2.0 × 6 m × 10 mm | 2 × 6 × 10 × 7.85 | 942.0 kg |
| 2.5 × 12 m × 20 mm | 2.5 × 12 × 20 × 7.85 | 4,710 kg |
| 300 × 300 × 20 mm base plate | 0.3 × 0.3 × 20 × 7.85 | 14.1 kg |
Quick reference: kg per m²
| Thickness (mm) | kg/m² |
|---|---|
| 3 | 23.55 |
| 6 | 47.10 |
| 8 | 62.80 |
| 10 | 78.50 |
| 12 | 94.20 |
| 16 | 125.60 |
| 20 | 157.00 |
| 25 | 196.25 |
| 30 | 235.50 |
| 40 | 314.00 |
| 50 | 392.50 |
Cut shapes
For profiles, compute the area of the shape and subtract holes:
- Circle: π × r²
- Annulus (flange ring): π × (R² − r²)
- Triangle gusset: ½ × base × height
Then multiply area (m²) × t × 7.85.
Other materials
| Material | Factor (kg per m² per mm) |
|---|---|
| Carbon steel | 7.85 |
| Stainless 304/316 | ~7.9–8.0 |
| Aluminium | ~2.7 |
Tolerance and actual weight
Mills roll within thickness tolerances (for example EN 10029 or ASTM A6), so actual plate weight can exceed theoretical. Agree the invoicing basis — see comparing steel quotations.
Try our steel weight calculator or browse steel plates.