Your BMR (Basal Metabolic Rate) is the minimum amount of energy your body requires to support the body's autonomic systems such as breathing, digestion, the nervous system, circulation, and regulation of body temperature. It can be used as an estimation of how much energy your body would burn if all you did was rest or sleep in a temperate and neutral environment for an entire 24 hour period of time.
This calculator uses the Mifflin-St Jeor equation which is a predictive equation derived from statistical data.
Factors that affect your BMR include age, genetics, weight, heredity, body fat percentage and gender. Knowing your BMR, and the factors that affect your metabolism, can help you with your goal to lose, gain or maintain your current weight.
Your BMR decreases with age because your muscle mass declines, so it becomes harder to stay trim.
Weight and height affects your BMR. The bigger you are, the more energy you need to sustain your larger organs. If you lose weight, your BMR goes down because you require less energy. On the other hand, if you build up your muscles, your BMR increases.
Body composition (ratios of lean body mass to body fat) differ between men and women. A women's BMR is typically 5 to 10% lower than man's.