I know what you mean.
Had to go back to fabric shop today and get 1/4 yd. more of three different fabrics just to cut out 2-3 more 5" squares for the I Spy swap because the clerk refused to straighten fabric as it came off bolt. When I 'squared' fabric after washing, I had to cut a piece off each end that measured from 1/'' to 3'' wide. So maddenening. So, I ended up short.
Yes, buy just a little more than you need.