Rebar weight estimator (bar schedule quantities)

Reinforcement is ordered and priced by weight, but drawings show diameters and lengths. The standard relationship for the density of steel is d²/162 kilograms per metre with the diameter in millimetres — the number every detailer keeps in their head. This estimator applies it to a bar mark, adds the lap and wastage allowance that turns a drawn length into an ordered length, and shows the tonnage.