Determining your body’s total dietary energy needs takes a bit of math — so grab a calculator. This method of determining your calorie needs is easier and almost as accurate as checking into a research lab and submitting yourself to scientific scrutiny by a white-coated nerd with a clipboard and a stopwatch.

1. Estimate your basic energy needs.

   Multiply your current weight (in pounds) by 10 if you’re a woman or 11 if you’re a man. Or use the formula in table below, which factors in your age in addition to your sex.

   For example: Sue is a 45-year-old female who weighs 155 pounds. She calculates her BMR like this:

   155 pounds ÷ 2.2 = 70.45 kilograms

   70.45 kilograms x 8.7 = 612.92 calories

   612.92 calories + 829 calories = 1,441.92 calories

   So Sue’s BMR — or the number of calories that her body needs at complete rest to function — is roughly 1,442 calories.

   If you figure Sue’s BMR by using the shortcut method, her needs are about 1,550 (155 pounds x 10 = 1,550) — a bit higher than the full calculation, but still in the same ballpark.

1. Determine your activity factor value.

   How active are you? Find the description in the following table that best matches your lifestyle. If you have a desk job but fit in a dose of daily exercise (at least 30 minutes), consider yourself in the light or moderate category.

1. Multiply your basic energy needs by the activity factor value that you determined in Step

   Using Sue as an example, she multiplies her BMR of 1,442 by 0.3 because her activity level is light — running around after her kids, taking care of the house, and fitting in a 2-mile morning walk with her neighbors every other day. Sue needs 432.6 calories for her activity level.

   1,442 x 0.3 = 432.6 calories

2. Determine the number of calories that you need for digestion and absorption of nutrients.

   Eating food actually burns calories. Digesting food and absorbing nutrients uses about 10 percent of your daily energy needs. Add together your BMR and activity calories and then multiply the total by 10 percent.

   The calculation for Sue’s calorie needs for digestion and absorption looks like this:

   1,442 calories + 432.6 calories = 1874.6 x 10% = 187.5 calories

3. Total your calorie needs.

   Add together your BMR, activity, and digestion/absorption calorie needs to get your total calorie needs — that is, the number of calories that you need to maintain your current weight.

   To maintain her current weight of 155 pounds, Sue calculates her total calorie needs like this:

   1,442 calories + 432.6 calories + 187.5 calories = 2,062 total calories