Hi. i'm a 16 year old inactive girl; 85 pounds and 5'2. how many calories should i eat a day?

Get active!: About 1600 calories per day but adjust according to your activity level.

Evolution: Don't worry about calories. Eat 2-4 meals and 1+ snacks each day composed of fresh produce, whole grains, nuts, seeds, beans, nontoxic seafood, lean beef/poultry, and whole fat dairy. Such a diet should provide sufficient macronutrients (protein, fat, carbs) and micronutrients (vit/minerals) to meet your daily needs. Although you are 'inactive' you need to find some daily activity you enjoy.