Coil Weight & Length
Weight and strip length of a coil from outer and inner diameter, width, thickness and density — or the OD a length or a target weight gives — with wraps.
Coil weight, strip length, number of wraps, weight per unit length and the batch totals; or the OD for a length or weight — annulus geometry with your density.
Example: A 1,500 / 508 mm coil, 1,250 wide and 1.5 thick at 7,850 kg/m³ weighs 15.35 t and holds 1,043 m in about 331 wraps (14.7 kg/m); 1,000 m of that strip winds to Ø1,461.
An annulus
of strip.
The coil model, the inverse solves, and where real coils differ.
The model
A coil is treated as a solid annulus: cross-section π/4 (OD² − ID²), so weight = annulus × width × density and strip length = annulus ÷ thickness (the same area seen as a long thin rectangle). Wraps ≈ (OD − ID) ÷ 2t and weight per metre = width × thickness × density.
Inverse solves
Given a length, OD = √(ID² + 4Lt/π); given a target weight, OD = √(ID² + 4m/(πWρ)). A coil count multiplies the totals.
Real coils
Strip has crown and the wrap is never perfectly tight, so real coils hold slightly less length per weight than the model — or more when the thickness runs on the plus side of its tolerance. Weigh one coil to calibrate; density is the value from your material certificate. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- weight = π/4 (OD² − ID²) × width × density; length = π/4 (OD² − ID²) ÷ thickness; wraps ≈ (OD − ID) ÷ 2t; OD = √(ID² + 4Lt/π) — tight-wound annulus model; density from the material certificate
Last reviewed 21 September 2026. How results are checked: How we verify.