I dont know, but a simple way is to use a thread pitch gauge, any machinist worth his salt should have one. Another way is to get the diameter over the threads with a micrometer or a pair of calipers. That will get you pretty close, then lay a scale ( accurate ruler, or use calipers) and count from thread crest to thread crest, for a easily determined amount....say 1/2 inch for US standard threads or say 10mm if you suspect its metric...( if its metric you either multiply or divide by 25.5 to determine what you want)
Hope this helps