pretty much the amount of calories you need to maintain your weight
credit to phate
find your bmr... basic metabolic rate.. its pretty much what your body needs to sustain it's weight if you were to do nothing all day
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
once you have that number, you can multiply it by an activity number to figure out your daily caloric expenditure, be honest here as this is the very cornerstone of your diet, if you are between two of the below activity levels then just multiply by a number in between them
To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:
If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9
.... do some math