Identifying Belt Specs for Cassette Players?

[cmiroc]

Does anyone know either:
(1) an extensive resource for finding specs for a replacement belt in a specific audio cassette device
OR
(2) how to find the right belt without resorting to trial and error?

I’m specifically looking to repair a General Electric 3-5300B “Compact Cassette Recorder.” Although it seems common, it’s not a deck I can find a matching belt for using my usual sources (webspareparts or fixyouraudio).

[amyk]

Measure circumference with string and subtract a few % for stretch.

[fzabkar]

Cut the old belt in half and measure its length. Take note of the thickness and cross-section.

[CaptDon]

You need to generate the specs then order accordingly. If round belt measure diameter and length. If square belt get dimension of square and length. If flat belt get width, thickness and length. To get accurate length you will destroy the old belt by cutting it and then measuring and then subtracting a certain percentage to compensate for the stretch that occurred over time. The get on a belt website and find the closest match. The place I use sells phonograph parts mainly but has also every belt I ever needed.