Steel Weight Calculator Formula

Understand the math behind the steel weight calculator. Each variable explained with a worked example.

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Formulas Used

Weight per Metre

weight_per_m = pi * pow(d_m, 2) / 4 * 7850

Total Weight

total_weight = pi * pow(d_m, 2) / 4 * 7850 * length

Quick Check (D^2/162)

quick_formula = pow(diameter, 2) / 162

Variables

VariableDescriptionDefault
diameterBar Diameter(mm)12
lengthTotal Length of Bars(m)100
d_mDerived value= diameter / 1000calculated

How It Works

Steel Bar Weight Calculation

Steel weight is calculated from the cross-sectional area, length, and density.

Formula

Weight per metre = (pi/4) x D^2 x rho

where D is the bar diameter in metres and rho is steel density (7850 kg/m^3).

Quick Formula

Weight (kg/m) = D^2 / 162 (where D is in mm)

This handy shortcut comes from simplifying pi/4 x (D/1000)^2 x 7850.

Worked Example

100 metres of 12 mm diameter rebar.

diameter = 12length = 100
  1. 01Weight per metre = pi/4 x (0.012)^2 x 7850 = 0.888 kg/m
  2. 02Quick check: 12^2 / 162 = 144/162 = 0.889 kg/m
  3. 03Total weight = 0.888 x 100 = 88.8 kg

Ready to run the numbers?

Open Steel Weight Calculator