You burn calories as you exercise and go about your daily activities. Your body also burns plenty of calories on its own just carrying out normal metabolic processes, such as digestion and circulation. You even burn calories while you sleep. To figure out how many calories your body burns each day, you will need to take into account your activity level and your weight. Generally, the more exercise you get and the more you weigh, the greater the number of calories you will burn.
Weigh yourself on a bathroom scale to determine your weight in pounds.
Assess your daily activity level. If you essentially sit at a desk all day at work, then on a couch all evening at home, consider yourself inactive. If your job involves a lot of walking or physical labor, or, for example, you go on long walks in the evening, consider yourself moderately active.
Multiply your weight in pounds by 10 if you are an inactive woman, by 12 if you are a moderately active woman, by 13 if you are an inactive man, or by 15 if you are a moderately active man. According to the University of Maryland Medical Center, or UMMC, the result is a good estimate of the baseline number of calories your body burns every day.
Add to your baseline total the calories from any strenuous exercises you do on a per day basis. For instance, if you work out on an elliptical machine today, add to your baseline the number of calories the elliptical's calorie meter indicates you burned while working out. This total represents the number of calories you have burned on this particular day.
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If you play a sport such as tennis or basketball, you can find resources that estimate how many calories you burn while doing so. MayoClinic.com contains a table listing the number of calories per hour people of varying weights typically burn while playing sports.
According to UMMC, "if you're more than moderately active, calorie needs may have to be adjusted so that you don't lose weight."