You could start with a known quantity of thread. The starting known quantity could be measured out on a swift or niddy noddy or warping board/reel. Then wind on to your spool and then count/measure the remainder. If you want to know the number of turns required to fill a certain amount, you can count as you go.

Also they do make yarn counters, but whether it would work for this would depend on the thickness and material of the thread.