Steel Weight Calculator
Calculate the weight of steel reinforcement bars from diameter, length and quantity using the d²/162 formula.
Formula last reviewed 4 August 2026 · How we verify our calculators
Total steel weight
53.33 kg
- Weight per metre
- 0.889 kg/m
Updates live as you type
Frequently asked questions
It is the standard way to find the weight of a steel bar per metre: weight (kg/m) = diameter² ÷ 162, with the diameter in millimetres. A 12 mm bar weighs about 0.888 kg/m.
It is derived from steel’s density (7,850 kg/m³) and the area formula, simplified into the constant 162 for convenience when the diameter is in mm and length in metres.
Multiply the per-metre weight by the length of each bar and the number of bars. Ten 12 mm bars of 6 m each weigh about 53.3 kg.
Yes, for round TMT/rebar of any diameter — 8, 10, 12, 16, 20, 25 mm and so on. Just enter the nominal diameter in millimetres.
Bump the bar size up one notch, and weight nearly doubles
A 12 mm bar, 6 m long, 10 bars: weight per metre is 12² ÷ 162 = 144 ÷ 162 = 0.889 kg/m, and multiplied by length and quantity, the total comes to 53.3 kg. Move up just one common size to 16 mm bars — same length, same quantity — and weight per metre climbs to 16² ÷ 162 ≈ 1.58 kg/m, nearly double. Because the formula squares the diameter, bar size has a far larger effect on steel weight, and therefore cost, than length ever does — length only scales linearly, diameter scales as its square.
The formula every estimator eventually needs, without re-deriving it
Steel is priced and sold by weight, but specified on drawings by diameter and length — the d²/162 formula bridges that gap, derived from steel's density of 7,850 kg/m³ and simplified into a single constant for convenience once diameter is in millimetres and length is in metres. This calculator applies it directly rather than requiring the formula to be looked up or re-derived on every estimate.
Why this matters beyond just getting a number
Knowing the weight in advance lets steel be priced accurately against the per-kg rate a supplier quotes, and lets delivered quantities be checked against what was actually ordered — a real check against both overcharging and short delivery, not just a planning nicety. It works for any standard round TMT bar size, from 8 mm stirrups up to 25 mm main bars.
This is an estimate for planning purposes. Always add a wastage margin and confirm exact quantities with your contractor or engineer before ordering materials. Laps, bends, cutting offcuts and rolling-margin tolerances all affect steel actually consumed on site, typically adding a further few percent on top of this raw calculated weight for a real structural job.