1. Health
You can opt-out at any time. Please refer to our privacy policy for contact information.

Body Mass Index (BMI)


Updated September 20, 2010

Definition: Body Mass Index or BMI is a calculation that determines weight status in adults by using your weight and height. The end result tells you if you're underweight, at a healthy weight, overweight or obese. A body mass index:
  • Over 40 is considered morbidly obese.
  • Over 30 is considered obese.
  • Between 25 and 29.9 is considered overweight.
  • Between 18.5 and 24.9 is considered a healthy bmi.
  • Under 18.5 is consider underweight.

BMI calculator

There are a few drawbacks to using BMI because it doesn't factor in:

  • How much muscle you have
  • Frame size
  • Gender
  • How your body fat is distributed

That means if you're very muscular, pregnant or have a large frame, your BMI calculation may show you as overweight or obese, even when you're not. How your body fat is distributed is also important for predicting your risk of heart disease, obesity-related illnesses and death. It's a good idea to use a variety of tools to determine how healthy your weight and body fat is including waist-to-hip ratio and/or your body fat percentage.

Related Video
Lower Body Toning with Lunges and Squats

©2014 About.com. All rights reserved.

We comply with the HONcode standard
for trustworthy health
information: verify here.