Work out coil length from weight instantly with clear inputs, formula shown and shareable results.
A coil's length follows from its mass, cross-section and density: length = weight / (width x thickness x density). Steel is 7850 kg/m3, aluminium 2700 and copper 8960. Weight per metre is the practical figure for setting blank counts against a coil.
Coil length
Length (m) = weight (kg) / (width (m) x thickness (m) x density (kg/m3))
Thickness tolerance is the main reason — a coil rolled at the top of its thickness tolerance is shorter for the same weight. Crown and edge trim also consume width.
Length = pi x (outer diameter^2 - inner diameter^2) / (4 x thickness), all in consistent units. It is useful when only the coil geometry is known.