About this calculator
Converts reinforcing bar diameter, length, and count into mass, for one or more bar entries.
Formula
volume per entry = (π / 4) × diameter² × length × count
mass per entry = volume × 7850 kg/m³ (steel density)
Mass per metre for a single bar reduces to the widely used rebar-table figure, e.g. for a 12 mm bar: (π/4) × (0.012 m)² × 7850 kg/m³ ≈ 0.888 kg/m — matching the commonly published value for 12 mm reinforcing bar.
Worked example
10 bars, 12 mm diameter, 6 m long each.
mass per metre = (π/4) × 12² × 7850 / 1,000,000 ≈ 0.8878 kg/m
mass per bar = 0.8878 × 6 ≈ 5.327 kg
total mass = 5.327 × 10 ≈ 53.27 kg
total length = 10 × 6 m = 60 m
FAQ
Does this calculator check whether the bar diameter or spacing is structurally adequate? No. This calculator only converts diameter, length, and count into mass — it does not check any structural requirement. Reinforcement design must be verified by a qualified engineer.
Why doesn't the calculator cite a standard?
7850 kg/m³ is the physical density of steel, a material constant, not a building-code value
— there is nothing to cite beyond that, so meta.standards is left empty.
Assumptions and limits
Assumes a plain solid steel cylinder — no allowance for ribs/deformations on the bar surface, which add a small amount of extra mass beyond the nominal diameter's own cylinder volume. Bar count, diameter, and length are exactly the values entered.