Calorie calculator basically tells you the amount of calories that you need to intake per day so as to achieve your required body goal.
In section 1, you enter your personal details such as age, gender, height and weight. The calculator uses these inputs and finds your total daily calorie expenditure.
In section 2, you enter your required goal ,i.e., maintain same level, gain or lose weight.
After this the Calorie Calculator finds the amount of calories you need to consume in a single day to achieve your target.
For achieving your desired calorie intake, refer to Nutrition and Health.