Every shop that I have been I can just take it to their cutting table and measure away,
I know the books suggest a min size repeat, but depending on the size of block that you are doing, you can use almost anything, it is more of the print that I look at, of course most people don't have my tendencies, (I tend to get carried away and cut them small, which is a habit that I am hoping to break in the near future) My smallest was strips cut at 1 3/4" I did do a bigger one or two as well.