Roll Length Calculator
How many metres are wound on a roll, from its outer diameter, core diameter and material thickness. Updates as you type.
mm
mm
µm
How roll length is calculated
The wound material forms a ring whose cross-sectional area, divided by the material thickness, gives the length:
Length = π × (OD² − core²) ÷ (4 × thickness)
Keep the units consistent (here diameters in mm, thickness in microns → metres). Because thickness is in the denominator, halving the gauge roughly doubles the metres on the same-size roll. To turn length into weight, use the roll weight calculator.
FAQ
How do you calculate the length of a roll?
Length = π × (OD² − core²) ÷ (4 × thickness), all in consistent units.
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