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Formula to Calculate Daily Caloric Intake

In order to gain or lose weight, you need to know how many calories you need simply to maintain what you have. You can calculate this basal metabolic rate easily, either by yourself or through using an online calculator. Armed with this information, you can then make smart decisions about diet and exercise to help bring your maintain you at your target weight.

  1. Basal Metabolic Rate

    • The basal metabolic rate, or BMR--that is, the amount of calories you need to sustain your current body weight--depends on your sex.

      For men, the BMR equals 66 + (6.23 X your weight in pounds) + (12.7 X your height in inches) - (6.8 X age in years). This value is then multiplied by an activity factor.

      For women, the BMR equals 655 + (4.35 X your weight in pounds) + (4.7 X your height in inches) - (4.7 X your age in years), with this result multiplied by an activity factor.

    Activity Factors

    • Selecting the right activity-factor multiplier is more of an art than a science. A sedentary lifestyle, which consists mostly of sitting, with almost no strenuous exercise, has a multiplication factor of 1.2.

      An extremely active lifestyle, which features daily aerobic exercise and manual labor, has a multiplication factor of 1.9.

      Between those extremes, a "lightly active" person multiplies by 1.375, a "moderately active" person by 1.55, and a "very active" person by 1.725.

      There are very limited guidelines on what puts a person into a specific category; this is mostly a self-assessment based on a person's normal physical activity. Very active people, like endurance runners, will fall at 1.9 or higher, and people who are couch potatoes are 1.2 or less. An average person who doesn't exercise but does engage in activities like some walking and housework will fall under the "lightly active" category.

    Examples

    • To put these formulas into perspective, consider Bob, a 33-year-old, lightly active male who weighs 190 lbs. and stands 5-foot-10. His daily caloric intake is as follows: (66 + (6.23 x 190) + (12.7 x 70) - (6.8 x 33)) x 1.375 = 2,632 calories.

      Or consider Helen, a 45-year-old, very active female who weighs 120 lbs. and stands 5-foot-6. Her daily caloric intake is: (655 + (4.35 x 120) + (4.7 x 66) - (6.8 x 45)) x 1.725 = 2,038 calories.

    Weight Changes

    • To gain or lose one pound of body weight, you need to consume 3,500 more or fewer calories than your basal metabolic rate requires over a defined period of time. For example, if Helen wanted to lose four pounds in a month, she would need to burn or consume 3,500 calories per week, or 500 in a day. To do this exclusively through diet modification, Helen should consume 1,538 calories per day for that week.

    A Tip

    • BMR is a formula based on an average person with an average metabolism. Some people have a higher or lower natural BMR based on their unique biochemistry, so these formulas may yield slightly different results for each person. Also, there are several different minor variations of the basic BMR formula, so different online calculators may yield slightly different results.

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