OK, here's a question I've never seen asked here. I wasn't sure which forum it belonged in, so I'm starting here.

I am holding a bolt of tartan for my organization that was custom woven for us. Some of it has previously been sold, so I'm not too certain how much tartan is there.

Do any of you know how to estimate the length of tartan on a bolt? I can measure the radius, diameter, and circumference of the circular bolt, and the tartan is probably a 12 or 13 oz weight. If relevant, it's double width. I was told there's about 40 yards on it, but no one knows for sure. I'm certainly not going to unroll it to find out!

Any thoughts? Thanks!