About this calculator
Use this calculator for solid square bar, rectangular bar and flat bar (patti). It gives the weight per metre for price lists and stock control, and the weight of each piece for cutting lists, transport and costing.
Formula
Square bar
A = a² m = A × L × ρ
a = side length, L = length (m), ρ = density (kg/m³). Quick rule for steel: kg/m = 0.00785 × a², with a in mm.
Rectangular / flat bar
A = w × t m = A × L × ρ
w = width, t = thickness, L = length (m), ρ = density (kg/m³). Quick rule for steel: kg/m = 0.00785 × w × t, with w and t in mm.
Worked example
Square bar: 20 mm carbon steel square bar. Area = 20 × 20 = 400 mm². Weight per metre = 400 × 10⁻⁶ × 7850 = 3.14 kg/m. A 6 m bar = 18.84 kg.
Flat bar: 50 × 10 mm steel flat. Area = 500 mm². Weight per metre = 500 × 10⁻⁶ × 7850 = 3.925 kg/m. A 6 m bar = 23.55 kg.
Assumptions and limitations
- Sharp corners at nominal size. Hot-rolled bars have slightly rounded edges, so real bars can be a little lighter.
- Rolling tolerances on width and thickness affect the real weight.
- Densities are typical values; check supplier data for your exact grade.
References
- Section area of a rectangle; steel mass based on 7.85 kg/dm³ as used in EN steel section tables.