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Calculate BMI

To calculate BMI, the only measurements you need are a person's height and weight. BMI is calculated the same way for both adults and children, but the criteria for interpreting the outcomes are different. You can calculate BMI by using the simple formula explained in the following article. The version of the formula you use to determine BMI differs depending on which system of measurement you're using.

 

Calculate BMI: An Overview

Research on obesity has shown that body fat can be assessed using a calculation called body mass index, or BMI. BMI does not measure body fat directly, but it correlates pretty closely to direct measures of body fat in most people.
 
The only measurements needed to calculate BMI are a person's height and weight. Because of this, BMI is an inexpensive and easy-to-use method of screening for weight categories that may lead to health problems (see Health Effects of Obesity).
 

What's the Formula Used to Calculate BMI?

BMI is calculated the same way for both adults and children. The BMI calculation is based on the following formula depending on whether you are using the metric system or the English system.
 
(Click on the BMI Calculator for another method of calculating BMI.)
 
Metric System
Weight in kilograms divided by height in meters squared (weight (kg) / [height (m)2]).
 
Since height is commonly measured in centimeters, divide height in centimeters by 100 to obtain height in meters before you use the formula.
 
To calculate BMI, take the weight (kg) and divide it by height (m). Then divide that number once again by height (m). Round to the second decimal place.
 
An example of calculating BMI using the body mass index formula: Height = 165 cm (1.65 m), Weight = 68 kg
 
BMI Calculation: 68 ÷ (1.65)2 = 24.98
(Calculate BMI Continued: Page 2)
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Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD