How many calories should I eat a day?

I'm 13 years old, and i weigh 94 pounds, give or take a couple pounds, but i'm chubby in the stomach. I know if I lose some of the belly fat my abs will show. I'm a teeny bit over 5"2, by the way. I want to be in good shape for the summer. How many calories should I take in a day? I don't do any sports, but I have a nice pool in my back yard and when i'm with friends (which is pretty often) we run around and have fun. Also, sometimes I go on my tread mill! So how should I eat to trim off about 2 inches of belly fat?