How to Calculate BMI: An Overview
Body mass index (
BMI for short) is an indirect measure of a person's body fat. The BMI formula is the same for both adults and children, as well as with different genders and ethnicity. However, the BMI formula does differ slightly depending on whether you are using the metric system or the English system.
How to Calculate BMI Using the Metric System
If you're using the metric system, the BMI formula is:
Weight in kilograms divided by height in meters squared (weight (kg) / [height (m)]2).
You can learn how to calculate BMI by taking the weight (kg) / [height (m) x height (m)]. Since height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters.
An example of calculating BMI using the BMI formula: Height = 165 cm (1.65 m), Weight = 68 kg
BMI Calculation: 68 ÷ (1.65)2 = 24.98
How to Calculate BMI Using the English System
With the English system, the BMI formula is:
Weight in pounds (lbs) divided by height in inches (in) squared and multiplied by a conversion factor of 703 (weight (lbs) / [height (in)2] x 703).
Therefore, to calculate BMI, take the weight (lbs) and divide it by height (in). Take the result of that calculation and divide it by height again. Then, multiply that number by 703. Round to the second decimal place.
An example of calculating body mass index using the BMI formula: Weight = 150 lbs, Height = 5'5" (65 inches)
BMI Calculation: [150 ÷ (65)2] x 703 = 24.96
(If you want to learn how to calculate BMI using another method, click BMI Calculator or BMI Chart. Also, click BMI and Weight for more information on what other factors healthcare providers consider when determining a person's risk for certain medical conditions related to weight.)
Add this article to your Favorites
Email this article
Print