› BMI Calculation

BMI Calculation

Body Mass Index

This page discusses the BMI calculation and what it is used for. If you are looking for the online BMI Calculator, then click here.

The BMI calculation is used as a screening tool to help medical personal gage if there is a health risk due to your weight.

This is not the only tool used as some people will fall into a higher risk category that are not potentially at risk

Based on their body size, fat percent and family history, a person may fall into the overweight category but are in fact at a healthy weight for them.

For example, a person with very little body fat and a larger percent of lean muscles may weigh than what is in the guidelines for their gender and height.

The Body Mass Index calculation will only show potential excess body fat and weight problems.

Additional tests and evaluations would also have to be performed to be certain. Your doctor may run additional tests such as a skin fold test to help measure the percentage of body fat. 

An evaluation of your diet, family history and activity level will also help measure your risk of weight related diseases.

Body Mass Index Definition

In order to understand the results of the BMI calculation you need to understand BMI. The definition of Body Mass Index is a number from the results of a calculation using a person’s weight and height. 

The results of the BMI formula are used as a tool to screen a person for potential weight problems due to body fat.

Excess weight and body fat could put a person at risk for certain diseases such as high blood pressure, high cholesterol and type 2 diabetes just to name a few.

The BMI calculator results will fall into one of four weight status categories; underweight, normal, overweight and obese. 

This status is used as an indicator of body fat. 

Although the Body Mass Index calculator does not measure the percentage of body fat, research has shown that the BMI results have a direct correlation to body fat percent.

The BMI calculator results will only show potential excess body fat and weight problems.

Additional tests and evaluations would also have to be performed to be certain. 

Based on the results of your doctor may run additional tests such as a skin fold test to help measure the percentage of body fat. 

Additionally, your doctor may evaluate your diet, family history and activity levels as well to measure your risk of weight related diseases.

Knowing the BMI Formula

BMI is calculated the same for adults and children. 

The results for adults however are not gender specific whereas the results for children and teens is age and gender specific.  

Note

For more on children and teens body mass index, visit cdc.gov for their BMI calculator.
For children and teens, the calculation is the same as below, but the results are interpreted using the age and gender percentiles. 


BMI Calculation

Pounds and inches

weight (lb) / [height (in)]² x 703

Example: Weight = 175 lbs
             Height = 5' 6" (66 inches)

Calculation = 175 / (66)² x 703 = 28.24

Kilograms & Meters

Weight (kg) / height (m)² 

Note:  Since height is generally measured in centimeters, divide height in cm by 100 to get the measurement in meters

Example weight = 80 kg
            height = 168 cm (1.68 m)  

Calculation = 80 / (1.68)² = 28.34

The results will fall into one of 4 categories. These are;

Class

BMI

Health Risk

Underweight < 18.5 Moderate
Normal 18.5 - 24.9 Minimal
Overweight 25 - 30 Moderate
Obese > 30 High

Within each class, there is a further break down by category.

Below is an outline of the categories within the classes.

Class    

Category

BMI

Health Risk

Underweight Severe Underweight < 16 Moderate
      Moderate Underweight 16 - 16.99 Moderate
      Underweight 17 - 18.49 Moderate
Normal Normal 18.5 - 24.9 Minimal
Overweight Overweight 25 - 26 Low
Moderately Overweight 27 - 29 Moderate
Obese Obese 30 - 34 High
Severe Obese 35 - 39 Very High
Morbid Obese 40 + Extremely High

Based on the results, your doctor may suggest some changes in diet and exercise.

What Steps Should You Take

If you find yourself within the normal range of the BMI results but still feel you want to lose or tone, then focus first on exercising and eating healthier.  Don't try to cut calories to lose weight but instead focus on losing inches and toning muscles.

However if your results are in the overweight or obese category then first check with your doctor to see if additional tests should be run.  

Also you will want to create a weight loss plan to lose weight and body fat.  Your plan should include eating healthy and exercising.  

Be sure to read these quick weight loss tips and exercise motivation tips to get you started on your weight loss program.

In addition to understanding the BMI calculation, read this article for the BMR calculation.

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