My calculations are that you would need 3.5 yards for 42 squares. Of course, only if your cutting is very precise. LQS prices, $9 and up. Some shops don't buy a whole collection so you would not find all the fabrics in a 'cake' in one shop. I don't like being restricted to a 10" piece of anything. I may like one or two of the pieces but would never think of buying the other fabrics if not in that set. I prefer whole yardage so I can use it for borders later in the project if so desired.