Originally Posted by JackB1
I use a 4 1/2 grip because I go by the old rule that says while gripping the racquet, you should be able to fit 1 finger in the remaining space between your thumb pad and finger tips.
The only rule I follow is 'use what feels comfortable'. That being said, I use a 4 1/2, and so do 90% of the people I play with. There are a few who use 4 3/8, but they are younger.
Oh, and how do I know what others use? Because I string their racquets & have on file what grip size the frame is.