i carry a pocket sized tape measure with me wherever i go and use it to measure my cuts right at the cutting table. i dont shop joanns very often at all because it is farther than i like but once the clerk had to recut 3 pieces of fabric because she didnt make sure it was straight and what i asked for. i stood at the counter and measured it showing her where her error was in making sure both ends were even before cutting but she wouldnt listen so recut she did.
i no longer wait until i get home to check my fabric cuts. i learned my lesson well to measure at the cutting table. my lqs will cut about 11 inches of fabric when i buy quarter cuts and about 6 inches of fabric when i buy an eighth of a yard cut (for my postage stamp quilts). i love them and they may give me an inch or so more if it is a clearance fabric.
ladies get you a small purse size tape measure to take with you when buying fabric. it is a wonderful tool to have.