Find the lenght of your fabric repeat, usually either 12" or 24", for a 12" repeat you will need 2 yards minimum, for a fabric with a 24" repeat you will need 4 yards minimum. Basically you need to stack 6 layers of matching fabric. There are lots of threads on OBW that probably explain it a little better plus there are other variables that go into how much fabric to get. Do you want to use some in borders?? or in the backing?? so many options, which adds to the fun of making them.