Article # 499. How to Convert BMI to Body Fat Percentage

Body mass index, or BMI, and body fat percentage are two different methods for determining a person's body type. BMI doesn't consider differences in fat or muscle mass. Therefore, a person with a muscular physique can be misclassified using BMI. Body fat percentage, however, gives a more accurate picture of body composition but is generally more time-consuming and expensive to determine. Since, BMI closely correlates with the amount of excess body fat, the body fat percentage can be estimated using the equations established and published in the British Journal of Nutrition in 1991 by nutrition researchers Paul Deurenberg, Jan Weststrate and Jaap Seidell. The formulas estimate the female body fat percentage to equal 1.2(BMI) + 0.23(age(y)) – 5.4 and the male body fat percentage to equal 1.2(BMI) + 0.23(age(y)) – 16.2.

Females


Step 1
Multiply your BMI by 1.2.

Multiply your age by 0.23.

Step 3
Add the result of Step 1 to the result of Step 2.

Step 4
Subtract 5.4 from the result of Step 3 to get your body fat percentage.

Males

Step 1
Multiply your BMI by 1.2.

Step 2
Multiply your age by 0.23.

Step 3
Add the result of Step 1 to the result of Step 2.

Step 4
Subtract 16.2 from the result of Step 3 to get your body fat percentage.