10.5" is okay but some of my fat quarters have wonky ends. By the time I get the ends straight and cut the 1" salvage off I only have enough for one 10.5" square. I m use to the 10" layer cakes. I understand the extra 1/2". It's just incase you wash the squares before use and you will have a little bit of shrinkage. This way you have 10" blocks if they do shrink after washing and drying.