How to estimate length of a roll (canvas, plastic film, etc.)?

This problem arises once you have to estimate the length of material in a roll without unrolling and spreading it for length measurement.

To solve the problem, you need to know the thickness of the material - T, take the measurements of the inside core on which the material is spun - d, and take the measurements of the outside roll dia - D.

Total length - L equals to the sum of each individual circumference length:

A.O. Chepok

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