ToolnozaRebar weight formula
For a nominal round steel bar, mass (kg) = π ÷ 4 × (diameter in metres)² × length (m) × quantity × steel density (kg/m³). This calculator uses a density of 7,850 kg/m³ and asks for diameter in millimetres, length per bar and bar count.
Example: ten 12 mm bars
A 12 mm diameter is 0.012 m. Ten bars of 6 m each give π ÷ 4 × 0.012² × 6 × 10 × 7,850 ≈ 53.27 kg. The estimated mass per metre is about 0.888 kg/m.
Use the specified bar length and count
Measure each straight bar length and multiply by the number of identical bars. For a cut-and-bent schedule, calculate each diameter and length group separately before adding totals. Overlaps, hooks and bends add steel length; do not omit them from a takeoff.
Estimate versus supplier weight
The formula treats the bar as a smooth circular cylinder. Ribbed reinforcing bars have nominal dimensions and manufacturing tolerances, so actual mass can differ. Use the applicable bar standard or supplier table for procurement, structural design and load limits.
Frequently asked questions
What density does the calculator use? 7,850 kg/m³ for steel. Does it include laps or hooks? Only if their lengths are included in your inputs. Is the result suitable for structural design? No; use approved drawings and local standards.