How metal weight is calculated
The weight of a bar, plate or tube is its cross-section times its length times the density of the material:
Weight = cross-section × length × density
Weight per meter (kg/m) = cross-section (mm²) × density (g/cm³) ÷ 1,000
| Shape | Cross-section |
|---|---|
| Plate, sheet, flat bar | A × B |
| Round bar | π ÷ 4 × A² |
| Square bar | A² |
| Hex bar (A across flats) | 0.866 × A² |
| Pipe, round tube | π ÷ 4 × (A² − (A − 2B)²) |
| Square or rectangular tube | A × C − (A − 2B) × (C − 2B) |
Worked examples
A carbon steel plate of 2,000 × 1,000 × 10 mm has a volume of 0.02 m³ and weighs 0.02 × 7,850 = 157 kg. A 20 mm round bar has a cross-section of 314 mm² and weighs 314 × 7.85 ÷ 1,000 = 2.47 kg per meter. In imperial units, carbon steel plate weighs 40.8 lb per square foot for each inch of thickness, so a 4 × 8 ft sheet of 1/4 in plate weighs 32 × 10.21 = 327 lb.
Weights of common sizes, carbon steel
| Size | kg/m | lb/ft |
|---|---|---|
| Round bar 10 mm | 0.617 | 0.414 |
| Round bar 20 mm | 2.466 | 1.657 |
| Round bar 1 in (25.4 mm) | 3.978 | 2.673 |
| Flat bar 50 × 10 mm | 3.925 | 2.637 |
| Square bar 25 mm | 4.906 | 3.297 |
| Pipe 60.3 × 3.9 mm (2 in Sch 40) | 5.425 | 3.645 |
Density 7.85 g/cm³. Mill tolerances change real weights by a few percent.
Densities of common metals
Carbon steel 7.85, stainless steel 304 7.93, stainless 316 7.98, cast iron about 7.2, aluminum 2.70, brass about 8.5 and copper 8.96 g/cm³. For loose bulk materials such as sand, gravel or ore, use the bulk material weight calculator.