Ok! This is all great info. Both stores I went to said they would cut as small as a four inch square - called an 8th? This is why I thought they might be able to do a specific size for me, but again, totally new!
The girl who we are making this quilt for wants solids only in dark reds, black, grey, tan, green, etc. She used scraps I think and had about 12 colours in her block, but some of them were different shades of colours. To keep my costs down, because these aren't colours I would typically use, I just want to try to spend as little as possible on fabric. I would be happy with probably 8 different colours or so.
Math is the hardest part of quilting by FAR!