How to calculate steel coil length and weight
A coil is just a long strip wound up, so everything starts from the weight per metre of the strip:
Weight per metre (kg/m) = Width (mm) × Thickness (mm) × 7,850 ÷ 1,000,000
From there:
- Length from weight: Length (m) = Coil weight (kg) ÷ Weight per metre
- Weight from length: Weight (kg) = Weight per metre × Length (m)
To estimate the wound-up size, the outer diameter follows from treating the coil as a flat spiral:
OD = √( ID² + 4 × t × L ÷ π ) (with the length L in mm)
where ID is the inner (eye) diameter and t the strip thickness. The calculator does all of this — just enter thickness, width and either the weight or the length.