It depends on the position he plays. Infielders use 11.5-11.75. outfielders use 12 and up.

He plays first base and pitches sometimes. If they need him in the outfeild he is a big takes it. But mainly first bast and he is an awesome first baseman. He was given this glove its a Rawlings 12.5 and seemed to do fine all season but it looked so big and now it is real loose, now yesterday someone gave him a glove and it is a 12.5 it just seems so big also. He is a big 9 year old,we were throwing the ball yestersay he seemed to be not catching as good with this one because of course it is not broken in. I no where the person got it should I take it backk and get a smaller one. He will be pitching and playing first base

At 9 I think 12.5 is way too big. Weight is most important as he will get tired
lugging around a heavy glove. At 9 I would go for 10.5 to 11 maximum.