What size bat for a 4 year old boy for tball?

Kathy

The smallest one you can find.

Randy

Let the t-ball team supply the bats for now. If your son plays in the minors, use the team's bats too. If your son goes on to the majors, then look for bats. That's about 4 or 5 years away. Then talk to parents and see what they got for their boys.