Could you explain how much calories do i need to eat per day?

Depends on your BMI: The amount of calories you need per day depends on you bmi, and if you want to keep the same weight, or loose weight or gain weight.And to maintain your weight you need to calculate your bmr, that is the number of calories you burn in a day. So average person need the equilant or thei BMR in calories for maitaining their weight neutral there are charts available to calculate your bmr.