The weight of a round steel bar depends only on its diameter and its length. On site the calculation is done with the d²/162 rule, which folds the density of steel (7850 kg/m³) into a single constant so the arithmetic can be done in your head.
Weight (kg) = d² × L / 162
d = bar diameter in mm, L = length in metres. The exact constant is 162.2; 162 is the site rounding.
Worked example
A 12 mm bar, 6 m long:
12² × 6 / 162 = 144 × 6 / 162 = 5.33 kg
A bundle of 20 such bars therefore weighs about 107 kg. For the full table of bar weights from 6 mm to 40 mm, and where the 162 comes from, read Unit Weight of Steel Bars: the d²/162 Formula, Explained.
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