|Sorry, this is sort of a 'negative' tip.
I purchase fabric from a variety of sources. I'm well pleased by the quality and service in the main. Some are internet businesses where I am not standing at the counter as material is measured.
Unfortunately twice I've run into yardage shortage. (Sometimes it's overage.) I did lots of figuring, planning etc based on the yardage on the receipt. This took quite a bit of time. But when it's short it's a big waste of time.
Once - 7 panels of curtains where 8 where needed. Lots of yardage here, hard to measure. Always ask if you are getting one piece of fabric. Not split. If they have no more of the fabric, you're sunk.
This morning, again I'm tracing pattern for a plaid with an icky 8 inch repeat. Ordered 3.5 yds - knowing plaid would be tough. Got 2 yds 32 inches. Argh. The other piece was measured over, paid for 2.75 yds, got 2.94. 18 inches in a plaid is like a mile in plain weave.
To be fair, the staff at these places may be rushed, or whatever and just slice at the approximate yardage. But approximate doesn't do on a plaid.
In both cases businesses took care of me for costs. But that did not save me any time.
Maybe everyone does this measuring except me. But now I will always measure the yardage first upon receipt. Won't figure, trace pattern until I do that. Saves time and reduces the aggravation.