How many calories a day to lose weight?

i am 18 years old female. i am 5feet .5inches and weight about 101lbs. i want to lose weight mainly cause of my calves because they are 14inches wide. i want to get it down to 13inches. i was wondering how much i should eat in one day. i usually go to the gym 3-4times a week and burn 500+ calories on the elliptical or hula hoop for an hour. how much should i be eating to lose weight and have my calves shrink?