Reel Length Calculator
How many meters of material a reel holds from its diameter, core diameter and material thickness, and the other way round: the diameter of a reel of a given length.
1 323 m
- core
- wound material (rings are layers; not all are drawn)
Length on the reel
1 322.5 m
Outer diameter
300.0 mm
Layers on the reel
2 238
How it is calculated
The wound material is a ring between the core and the outer edge. Its area is π × (D² − d²) ÷ 4 and the material is t thick, so the length L = π × (D² − d²) ÷ (4 × t).
The other way round: D = √(d² + 4 × t × L ÷ π). All sizes are in millimeters, the length is shown in meters.
L = π · (D² − d²) / (4 · t) D = √(d² + 4 · t · L / π)
Worked example
D = 300 mm, d = 76.2 mm, t = 0.05 mm.
L = π × (300² − 76.2²) ÷ (4 × 0.05) = π × 84,193.56 ÷ 0.2 ≈ 1,322,508 mm ≈ 1322.5 m.
Theoretical: a real reel is wound less tightly (there is air between the layers), so it holds fewer meters. An estimate.
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