How to calculate steel weight
The weight of any steel section comes from three things: its cross-sectional area, its length, and the density of the material. The formula is:
Weight per metre (kg/m) = Cross-sectional area (mm²) × Density (kg/m³) ÷ 1,000,000
Carbon steel has a density of 7,850 kg/m³. Multiply the weight per metre by the length and the number of pieces to get the total weight. The calculator above does this automatically for the most common profiles.
Common steel densities
| Material | Density (kg/m³) |
|---|
| Carbon / Mild Steel | 7,850 |
| Stainless Steel | 8,000 |
| Aluminium | 2,710 |
| Brass | 8,500 |
| Copper | 8,960 |
Quick reference — weight per metre
| Section | Example size | Approx. weight |
|---|
| Round bar | Ø20 mm | 2.47 kg/m |
| Rebar | Ø16 mm | 1.58 kg/m |
| Plate | 100 × 10 mm | 7.85 kg/m |
| Equal angle | 65 × 65 × 6 mm | 5.91 kg/m |
| SHS tube | 80 × 80 × 3 mm | 7.16 kg/m |
Frequently asked questions
How do you calculate the weight of steel?
Steel weight is the cross-sectional area of the section multiplied by its length and the density of steel (7,850 kg/m³ for carbon steel). Weight per metre equals area in mm² × density ÷ 1,000,000, and total weight is weight per metre × length × quantity.
What density should I use for steel?
Use 7,850 kg/m³ for carbon and mild steel. Stainless steel is about 8,000 kg/m³, aluminium about 2,710 kg/m³. Switch the Material dropdown above to match your section.
How do you calculate rebar weight?
Rebar weight per metre is the diameter squared divided by about 162 (the D²/162 rule), or more precisely the circular area × steel density. A 16 mm bar is about 1.58 kg/m. Pick "Reinforcement Bar" above and enter the diameter.
Is this calculator free?
Yes — completely free, no login required. For a full BOQ generated from your actual drawings, SteelConnect's AI estimation gives you a free first estimate.