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BMI Calculation

An accurate BMI calculation can be obtained by using the body mass index formula. The same result can also be arrived at using a BMI calculator or chart -- these methods do the math for you. Regardless of which method you use, the only measurements needed to calculate BMI are a person's height and weight. Because the BMI calculation only requires these two measurements, it is an inexpensive and easy way to screen for weight categories that may lead to health problems.

 

BMI Calculation: An Overview

Researchers studying obesity have determined that a person's level of body fat can be measured using a simple calculation known as body mass index (BMI). While BMI is an indirect measure of body fat, it does correlate 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 the BMI calculation only requires these two measurements, it is an inexpensive and easy way for healthcare providers and the general public to use as a method of screening for weight categories that may lead to health problems (see Health Effects of Obesity).
 

BMI Calculation: Specifics

BMI calculation is done the same way for both adults and children. The formula used for BMI calculation differs somewhat, depending on whether you are using the metric system or the English system.
 
(You can also click on the BMI Calculator or the BMI Chart to determine your BMI.)
 
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]).
 
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 BMI calculation: Height = 165 cm (1.65 m), Weight = 68 kg
 
BMI Calculation: 68 ÷ (1.65)2 = 24.98
(BMI Calculation Continued: Page 2)
Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD