Your BMR is the amount of energy your body needs to function. We use about 60% of the calories we consume each day for basic bodily functions such as breathing.
Other factors that influence your BMR are height, weight, age and sex. (Please note that this formula applies only to adults.)
Step one is to calculate your BMR with the following formula:
655 + (4.3 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
66 + (6.3 x weight in pounds) + (12.9 x height in inches) - (6.8 x age in years)
The resulting number of each equation is your BMR.
Step two: In order to incorporate activity into your daily caloric needs, complete the following calculation:
If you are sedentary: Multiply BMR x 20 percent
If you are lightly active: Multiply BMR x 30 percent
Add this number to your BMR. This resulting number is the number of calories you can comfortably consume each day without weight gain.
Ready to get started with losing weight by calorie counting? The helpful tools at About.com's Calorie Count can help you track your calorie needs and your calorie use throughout the day. For free!