Instead, squash players all start with the same grip size and then build their racquet handles up to the size they want by using a combination of grip and overgrip.
Many players are satisfied with a single grip. Some, with larger hands, will add an additional layer or two of overgrip while players with extremely large hands will often begin with two layers of grip followed by one or more layers of overgrip.
Only the highest quality squash racquets come outfitted with proper grip when you bring them home from the store. Most racquets, in fact, come with a very thin rubber wrapping that looks like grip. This is not a grip and should be replaced immediately. Even good quality racquets will usually require the installation of grip and string before you can play squash with them.
So how much grip and/or overgrip should you wrap around the handle of your new squash racquet?
To find out, hold the racquet in your hand as you would when you play. The squeeze the handle as tightly as you would if you were about to make contact with the ball.
The tips of your fingers should be barely touching your palm below your thumb. If they are pressing into your palm, the grip is too small. If they are unable to reach your palm, the grip is too large. Add or remove a combination of grip and/or over grip until it is the perfect size for your hand.