My quilts end up the size they end up. By that I mean that I can never "plan" a size because it just won't happen. I pick a block and plan the block. Based on that, I do a layout on grid paper until I have the right proportions (intuitively). Once that is sewn, I decide on the borders. Again - intuitive decision coupled with how much fabric I have. And yes, I have ended with some odd-sized tops before. lol