Body mass index (BMI) is calculated using height and weight and is scaled to determine an approximation of body fatness, for both male and female adults. BMI has limitations, because muscle weighs more than fat, therefore, some highly muscled individuals may have a high BMI and not be conventionally considered overweight. Basal Metabolic Rate (BMR) is the number of calories a person needs to keep their basic body functions working, without moving. BMR can be combined with activity level to calculate the number of calories needed in a day for weight control. BMR is gender-related and decreases with age.
Body Mass Index (BMI)
Step 1
Square your height (in inches). Example: 65 inches squared = 65x65 = 4225
Step 2
Divide your weight by your height squared. Example: 140 lbs/4225 = .033
Step 3
Multiply the result by 703. Example: .033 x 703 = 23.19. This number is your BMI.
Step 4
Understand your BMI results: A BMI below 18.5 is considered underweight; a BMI between 18.5 and 24.9 is considered normal weight; a BMI between 25 and 29.9 is considered overweight; and a BMI above 30 is considered obese.
Basal Metabolic Rate (BMR)
Step 1
Add 655 to your weight in pounds, multiplied by 4.35 if you are female. Example: 655 + (140 x 4.35) = 1264.
Add 66 to your weight in pounds, multiplied by 6.23 if you are male. Example: 66 + (180 x 6.23) = 1187.4.
Step 2
Add the result to your height in inches, multiplied by 4.7, if you are female. Example: 1264 + (65 x 4.7) = 1569.5
Add the result to your height in inches, multiplied by 12.7, if you are male. Example: 1187.4 + (70 x 12.7) = 2076.4
Step 3
Subtract from the result your age in years, multiplied by 4.7, if you are female. Example: 1569.5 - (35 x 4.7) = 1405
Subtract from the result your age in years, multiplied by 6.8, if you are male. Example: 2076.4 - (35 x 6.8) = 1838.4
This result is the number of calories that your body needs at rest to maintain your current weight.
Tips and Warnings
- BMR is the number of calories needed to maintain your current body weight while not moving. Once you know your your BMR, you can also calculate your daily caloric needs based on your activity level using the Harris Benedict Equation: To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows: Little or no exercise = BMR x 1.2; light exercise/sports one to three days a week = BMR x 1.375; moderate exercise/sports three to five days a week = BMR x 1.55; hard exercise/sports six or seven days a week = BMR x 1.725; very hard exercise/sports and a physical job = BMR x 1.9.
- BMI is only one factor in determining overall health. It is a general guide and should be used in conjunction with other factors such as waist circumference.
Things You'll Need
- Scale
- Measuring Tape
- Calculator
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