Free tool
Steel weight calculator
Calculate the theoretical weight of steel bar, plate, sheet, coil, pipe, and tube in kilograms and tonnes. Switch material for carbon, stainless, alloy, aluminium, or copper.
Steel weight calculator
Weight per metre
2.47 kg/m
Weight per piece
14.80 kg
Total weight
1.480 t
1,479.69 kg
Calculated as cross-sectional area (π/4 × diameter²) × length × density (7850 kg/m³). This is theoretical weight — the number a mill uses to bill you. Always reconcile it against the actual weighbridge weight on delivery.
Steel weight formulas
Every result uses weight = cross-sectional area × length × density (ρ). For carbon steel ρ = 7850 kg/m³.
| Profile | Formula | Notes |
|---|---|---|
| Round bar | π/4 × D² × L × ρ | D = diameter (mm), L = length (m) |
| Square bar | a² × L × ρ | a = side (mm) |
| Flat bar / plate | W × T × L × ρ | W = width, T = thickness (mm) |
| Round pipe | π/4 × (OD² − ID²) × L × ρ | ID = OD − 2 × wall |
| Square tube | (outer − inner area) × L × ρ | hollow section |
Frequently asked questions
How do you calculate the weight of steel?
Steel weight equals the cross-sectional area of the profile multiplied by its length and the material density. For carbon steel the density is 7850 kg/m³. For a round bar, weight per metre = π/4 × diameter² × density, with the diameter in metres. This calculator does that automatically for bars, plate, sheet, pipe, and tube.
What is the theoretical weight of steel?
Theoretical weight is the weight calculated from nominal dimensions and standard density — the figure a mill uses to bill you. It differs from actual (weighed) weight because real bars can be rolled slightly under or over their nominal size. When steel is rolled to the low end of tolerance, theoretical-weight billing quietly delivers less metal than you paid for.
What is the density of steel used in the calculation?
Carbon and mild steel is 7850 kg/m³. Stainless steel is around 8000 kg/m³, aluminium is 2700 kg/m³, and copper is 8960 kg/m³. This calculator lets you switch material so the density is applied correctly.
Should I pay on theoretical or actual weight?
For coil, plate, and rebar from China, insist on settlement by actual weighbridge weight, or agree a tight tolerance in the contract. Paying purely on theoretical weight is a common way buyers end up short — always reconcile the calculated figure against the weighed delivery.
Worried the delivered weight won't match?
Learn how short-weight scams work and how to reconcile theoretical vs actual weight.