The number of calories you need each day depends on your activity levels and your body size. Your diet is the key factor that affects your weight and health.
How many calories do I need a day I found that according to the US Department of Agriculture inside of My Pyramid, they recommended the follow number of calories per day that you should eat:
For persons who get less than 30 minutes of moderate physical activity every day the numbers of calories are:
Children------ 2-3 years old : 1000 calories
Children------ 4-8 years old : 1200-1400 calories
Girls ----------9-13 years old : 1600 calories
Boys ---------9-13 years old : 1800 calories
Girls --------14-18 years old : 1800 calories
Boys --------14-18 years old : 2200 calories
Females ----19-30 years old: 2000 calories
Males -------19-30 years old : 2400 calories
Females ----31-50 years old: 1800 calories
Males --------31-50 years old: 2200 calories
Females -------51+ years old:1600 calories
Males -----------51+ years old:2000 calories
Children --------2-3 years old : 1000-1400 calories
Children --------4-8 years old : 1400-1800 calories
Girls ------------9-13 years old : 1600-2200 calories
Boys -----------9-13 years old : 1800-2600 calories
Girls -----------14-18 years old : 2000-2400 calories
Boys ----------14-18 years old : 2400-3200 calories
Females ------19-30 years old: 2000-2400 calories
Males ---------19-30 years old: 2600-3000 calories
Females ------31-50 years old: 2000-2200 calories
Males ---------31-50 years old : 2400-3000 calories
Females ------- 50+ years old :1800-2200 calories
Males -----------50+ years old : 2200-2800 calories
Check out your daily caloric needs for your goal weight.