To track amounts, I estimate. First less than 1/4 yd goes into scraps of small pieces box and I don't keep track of them. When I get too much to store, I give them to a person who like very scrappy quilting.
So after I've made the front and back; I consider how much is in the back, add amount for binding and double that. If that seems off yardage for the front I adjust up/down. Since there's probably x0,000+ yds in my stash 1/2 yd off isn't an issue right now. When it's down to x000 yds, I'll keep it more accurate