When I had more money than time I used to buy two to three yards. Now that I am actually making quilts I have found that for a Queen sized bed quilt three yards is good for the focus fabric and one to two yards for the other colors. I am finishing a quilt that called for five different fabrics so this formula worked well with it. Most non-scrappy quilt patterns ask for four of five different fabrics so this 'system' has worked well for me. Backs are a differnet story but more and more I am even piecing the back. Hope this helps although in truth I'm like most quilters "Never enough fabric".