How To Calculate Calories Needed To Maintain Weight

Calculating calories needed to maintain weight actually takes two calculations. First you'll need to calculate basal metabolic rate (BMR), which is the amount of energy expended while at rest, or more simply put, the amount of calories burned if you lay in bed all day. The reason the second equation is needed is because most people do not lie in bed all day. The Harris Benedict equation, as it is called, uses the BMR output and calculates activity to determine the calories needed to maintain weight based on activity levels.

Step 1

Enter height, weight and age into the appropriate equation based on gender. BMR decreases with age and loss of lean body mass, which means that as you age, your maintenance calories will drop as well. Men: BMR = 66 + (6.23 * weight in pounds) + (12.7 * height in inches) -- (6.8 * age in years). Women: BMR = 655 + (4.35 * weight in pounds) + (4.7 * height in inches) -- (4.7 * age in years).

Step 2

Determine your activity level. A sedentary person gets little or no exercise. A lightly active person participates in light exercise or sports one to three times per week. A moderately active person performs moderate intensity exercise or sports three to five times per week. A very active person is involved in hard exercise or sports six to seven times per week. An extra active person completes very hard exercise or sports and has a physical job every day, or trains two times a day.

Step 3

Multiply your BMR by the appropriate activity factor. Sedentary = BMR * 1.2; Lightly active = BMR * 1.375; Moderately active = BMR * 1.55; Very active = BMR * 1.725
Extra active = BMR * 1.9. One factor that isn't included in the Harris Benedict equation is lean body mass; therefore, this equation is inaccurate for those who are very muscular or very fat.