for those of you who don't want to bother with math, and who, by mistake, made a 9 patch too small for the intended purpose, here's an option...sew a coordinating fabric strip to TWO sides of your finished 9 patch, then cut both ways as before and rearrange. The extra strip gives more interesting options in placement...and you don't waste that orphan block. Once you try one, it might become interesting enough to make into a whole quilt. You can either be precise and measure the difference between what you have any what you want, calculate seam allowances then cut and sew the strips on...or do what I did and cut extra strip wide enough to accommodate what I would need and sized the block up after I'd finished the new block.