How many calories does an 11-year-old boy need per day?

Hi! im ash im 11 years old to i dont really watch my calories but i look on food boxes and if its high in calories i make sure to move around after i eat. Im having truble with my waight cause if i gain a little fat on my legs it runs in my family u can EVER lose it so i really watch what i eat! SMILL BE HAPPY!