I always try to decide will I use it as focus, background, complimentary, or borders. If its focus, background, or complimentary at least 1 1/2 yd each. If its borders at least 2 1/2 yd. and if its backing at least 4 1/2 yd. Also the more fabrics you have in a quilt the less you'll need of each one. This is all based on lap-size quilts which is what I make the most of.