Introduction
The weight of a steel bar, plate or tube is its cross-section area times its length times the density of the metal. Steel weighs 7 850 kg per cubic metre, so a 20 mm round bar weighs 2.47 kg per metre, and a 10 mm plate 78.5 kg per square metre. The numbers matter for ordering, transport, lifting and the dead load in a structure.
This calculator gives the cross-section, weight per metre and per foot, weight per piece and total weight of the common shapes: plate, round, square, hex and flat bar, round and rectangular tube, angle, I-beam and channel. It covers carbon and stainless steel, aluminium, copper, brass, bronze, cast iron, titanium and lead, or any density you enter.
Formulas
Weight of n pieces of length L:
m = ρ × A × L × nCross-section areas:
plate, flat bar: A = w t
round bar: A = π d² / 4
hex bar: A = (√3 / 2) s² s across flats
round tube: A = π t (D − t)
rectangular tube: A = b h − (b − 2t)(h − 2t)
angle: A = t (a + b − t)
I-beam, channel: A = 2 b t_f + (h − 2 t_f) t_w- ρ — density: carbon steel 7 850, stainless 304 7 900, aluminium 2 700, copper 8 940 kg/m³
- D, t — outside diameter and wall of a tube; b, h — width and height
Assumptions and limitations
- Weights are theoretical, for sharp-cornered shapes. Hot-rolled angles, beams and channels have root fillets, and tubes have rounded corners, so catalogue weights differ by a few percent. Use the catalogue weight for standard sections where it matters.
- Mill tolerances on thickness allow the real weight to vary by up to about 5 %.
- Enter the actual outside diameter of a pipe, not its nominal size: 2 in pipe is 60.3 mm (2.375 in) outside.
- Alloy densities vary by one or two percent. Enter a measured or catalogue density for exact work.
Worked example
What does a 6 m length of 20 mm diameter steel round bar weigh?
- Area: π × 20² / 4 = 314.2 mm² = 0.0003142 m².
- Weight per metre: 7 850 × 0.0003142 = 2.466 kg/m, or 1.657 lb/ft.
- Weight of the bar: 2.466 × 6 = 14.80 kg.
A bundle of 20 such bars weighs 296 kg.
FAQ
How do I calculate the weight of steel?
Multiply the volume in cubic metres by 7 850 kg/m³. For a bar, the volume is the cross-section area times the length.
How much does a steel plate weigh per square metre?
7.85 kg per millimetre of thickness: 78.5 kg/m² for 10 mm, 157 kg/m² for 20 mm. In US units, 40.8 lb/ft² per inch of thickness.
Is stainless steel heavier than carbon steel?
Slightly: 304 is about 7 900 kg/m³ and 316 about 8 000 kg/m³, against 7 850 for carbon steel.
How much lighter is aluminium?
About a third of the weight of steel for the same shape: 2 700 against 7 850 kg/m³.
What is the weight of steel pipe per metre?
Use the outside diameter and wall: 60.3 × 3.9 mm (2 in Schedule 40) is 5.43 kg/m.
Why does my supplier's weight differ?
Catalogue weights include root fillets and corner radii, and suppliers sometimes quote the maximum weight within tolerance. Differences of 2 to 5 % are normal.
Related calculators
- Rebar weight and quantity — reinforcing bars by size.
- Moment of inertia (section properties) — stiffness of the same shapes.
- Concrete volume and rebar weight — concrete with its reinforcement.
- Lifting sling — rigging for the weight.