Several people have explained this, in different ways, so let me try again in yet another way. The first (very long)strip is 2" wide (finished). After halving and sewing two together, you have one that is 4" wide. Then 8", 16", 32", 64", 128", 256", 512", etc. (now that would be a BIG quilt!) The length doubles every time you sew two halves together. So, not many lengths to choose from, if you're making the quilt in the traditional way. And the only lengths that actually make much sense are 32", 64", and possibly 128" for large kingsize. Really, I think the jelly roll race is meant to be a novelty, made-for-fun quilt. Sometimes it comes out beautiful, and other times not so much, because you don't get to choose where the fabrics meet.