how big to make the starting chain loop

So I was just thinking and decided to post this. When crocheting something that you have to chain a loop an easy way to know how many chains the loop needs to be is do one chain for every 3 stitches that will be stitched into the loop. Like a 4 sided granny square would have a ch4 and slip stitch to form loop then you would put 4 3dc clusters into that chain 4 loop. This is what works for me anyway.