Okay, nevermind. I sat down to go through this again before trying a test block and.... the numbers were correct. I was confusing finished size with unfinished size. Once I added up all the pieces and then subtracted the seams it all worked out. Just came on here to say don't listen to a little bird when it comes to math. Sigh! Thank you, Dunster. Will have a look at your diagram. Trial block after dinner. So good to go through these mental exercises, someday it will click. I hope.