Steel Weight Calculator in kg and Tonnes
Pick a section, enter its size in millimetres and the length in metres. You get the weight per metre, per piece and in total, for steel, stainless steel or aluminium.
Steel weight calculator
- Weight per metre
- Weight per piece
- Total in tonnes
- Cross-section area
How steel weight is calculated
Weight is volume multiplied by density. The calculator finds the cross-section area, multiplies by the length, and applies the density of the material:
weight (kg) = area (mm²) × length (m) × density (kg/m³) ÷ 1,000,000
For mild steel that is area × 0.00785 kg for every metre.
Area formulas
| Section | Area |
|---|---|
| Round bar, rebar | π × d² ÷ 4 |
| Square bar | side² |
| Flat bar, plate | width × thickness |
| Round pipe | π × (OD² − ID²) ÷ 4, where ID = OD − 2 × wall |
| Hollow section | width × height − (width − 2 × wall) × (height − 2 × wall) |
| Angle | (leg A + leg B − thickness) × thickness |
Rebar weight per metre
For round bar the formula reduces to the site rule d² ÷ 162, with the diameter in
millimetres.
| Diameter | kg per metre | 12 m bar |
|---|---|---|
| 8 mm | 0.395 | 4.74 kg |
| 10 mm | 0.617 | 7.40 kg |
| 12 mm | 0.888 | 10.65 kg |
| 16 mm | 1.578 | 18.94 kg |
| 20 mm | 2.466 | 29.59 kg |
| 25 mm | 3.853 | 46.24 kg |
| 32 mm | 6.313 | 75.76 kg |
Hollow sections and angles are calculated with square corners. Rolled sections have rounded corners, so manufacturers' tables can differ by a few percent. Use the supplier's figure when you order.
Steel Weight Questions
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