The basal metabolic rate (BMR) is scientifically defined as the minimal rate of energy expenditure per unit time by endothermic animals at rest. In lay terms, it is a measure to determine the amount of energy that is spent just resting in a neutrally temperate environment, such as if you decided to lay in bed all day.
Determining your BMR is important because it can give you an idea of how many calories that you should consume each day just to stay alive. When you are trying to exercise and eat right to lose weight, netting at least your BMR is non-negotiable because your body eventually will think you are starving if caloric intake isn’t meeting energy requirements. As your body tries to figure out how to deal with the perceived starvation, it can use stored carbohydrates, fat or protein for energy sources.
To calculate your BMR, you can plug your information in the following equations, or you can head to Bodybuilding.com
Women: BMR = 655 + (4.35 x weight(lbs)) + (4.7 x height(in)) – (4.7 x Age(yrs))
Men: BMR = 66 + (6.23 x weight(lbs)) + (12.7 x height(in)) – (6.8 x Age(yrs))