Body Mass Index Formula

Using the Metric System

With the metric system, the body mass index formula is:
 
  • Weight in kilograms divided by height in meters squared (weight (kg) / [height (m)2]).
 
Since height is commonly measured in centimeters, divide your height in centimeters by 100 to obtain your height in meters before you use the formula.
 
To calculate BMI, take your weight (kg) and divide it by height (m). Then divide that number once again by height (m). Round to the second decimal place.
 
Here's 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.
 

Using the English System

With the English system, the 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 your weight (lbs) and divide it by your 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.
 
Here's an example of calculating BMI using the formula: Weight = 150 lbs, Height = 5'5" (65 inches):
 
BMI Calculation: [150 ÷ (65)2] x 703 = 24.96.
 
(To automatically determine your BMI, click on the BMI Calculator. You can also use the BMI Chart to calculate your BMI.)
 
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