When I first started quilting in 1992, I would buy a quarter yard. Now, it's no less than two yards of any one fabric for a very good reason. I have lots of variety, and not much of any one thing. When I get ready to do a large quilt, I know I will not have much, so the quilt ends up being smaller. When I plan a quilt in advance of buying the fabric, I use a calculator to figure how much I will need, and then get an extra half yard.