I just measure my quilt (through the center) to get the border size then I just figure out how big to make my piano keys to fit that measurement - for instance if the quilt is 60" then I would figure that 30 - 2" keys would work - (of course they are cut at 2 1/2" for seam allowance) then I just pick random colors from the quilt - I have made all sizes of keys - just whatever fits the border - so far it works.