How To Calculate Minimal Caloric Intake

When beginning a weight-loss regimen, the usual first step is to cut calories. However, if you don't know how many calories you burn to begin with, it's hard to figure out exactly how much you're cutting through exercise or diet. The Harris-Benedict Equation below gives you that information. The first three steps calculate your body's Basal Metabolic Rate (BMR), which is the number of calories your body burns just existing during the course of a day. In Step 4, you use your BMR to calculate how many total calories you burn by taking your daily activity level into account.

Step 1

Calculate the weight component.

Men: 66 + (6.3 times your weight in lbs.)

Women: 655 + (4.3 times your weight in lbs.)

Example: A 145-pound woman would calculate her weight component as follows: 655 + (4.3 times 145) = 1278.5.

Step 2

Using the weight calculations, add the height component.

Men: Step 1 total + (12.9 times your height in inches)

Women: Step 1 total + (4.7 times your height in inches)

Example: If our 145-pound woman is 5 feet, 5 inches tall, she would calculate this as follows: 1278.5 + (4.7 times 65) = 1584.

Step 3

Using your weight and height calculations, add the age component to complete your BMR.

Men: Step 2 total - (4.7 times your age in years) = BMR

Women: Step 2 total - (4.7 times your age in years) = BMR

Example: If our sample woman is 30 years old, her final BMR calculations would be as follows: 1584 -- (4.7 times 30) = 1443. This represents the number of calories she would burn just by existing.

Step 4

Find the category that best describes your activity level, and complete the calculations using your BMR from Step 3.

Sedentary: BMR + (BMR times .20)

Lightly Active, 1 to 3 days per week: BMR + (BMR times .375)

Moderately Active, 3 to 5 days per week: BMR + (BMR times .55)

Very Active, 5 to 7 days per week: BMR + (BMR times .725)

Athlete, two heavy workouts per day: BMR + (BMR times .90)

If our 145-pound, 30-year-old woman from above were very active, the number of calories she would burn daily would be as follows: 1443 + (1443 times .725) = 2489.175, or 2489 calories per day.

Using this information, you can decide how to combine cutting calories with exercise to achieve your desired weight loss.

Tips and Warnings

Use a calculator to do the math, and keep track of your calculations by writing them on a piece of paper. Keep this number handy for future reference.
Although this calculation is fairly accurate for most people, it can underestimate the number of calories burned by a highly fit person with a very low percentage of body fat. Likewise, the formula can also overestimate the number of calories burned by an unfit, obese individual with a high percentage of body fat.