On this page is a BMI Calculator. BMI, or Body Mass Index, is a measure of whether a person is at a healthy weight.
Body Mass Index Calculator
Body Mass Index Formula
This calculator is based on the Body Mass Index Formula. To compute body mass index, first (if needed) convert weight to kilograms and height to meters.
Weight in Kilograms
(Height in Meters) ^ 2
Body Mass Index Guidelines
This calculator uses the United States Center for Disease Control guidelines for healthy BMI.
CDC BMI Categories
- < 18.5 Underweight
- 18.5 – 25 Healthy Weight
- 25 – 30 Overweight
- 30 and up Obese
Categories of Obesity
One BMI is in the obese category, the CDC categorizes levels of obesity. There are currently three levels:
- 30 – 35 Class 1 Obesity
- 35 – 40 Class 2 Obesity
- 40 and up Class 3 Obesity
- Also known as extreme or severe obesity
BMI as a Measure of Health
For some percentage of people, BMI inaccurately classifies them as healthy or unhealthy. While Body Mass Index is an excellent measure at a population level, it does occasionally fail for individuals.
Adding additional variables can help sort out false categorizations.
Popularly, body fat percentage gives a better sense of healthy body composition. An athlete with low body fat and high levels of muscle might be improperly classified as overweight or obese. Likewise, a person with low levels of muscle but a normal weight might have an unhealthy body composition. As muscle mass varies with age, the effect becomes more extreme at lower and higher ages.
How Should You Use BMI and the BMI Calculator?
This calculator isn’t health advice. If you are concerned about body composition and health you should consult a doctor, nutritionist, or other qualified professional.
Additionally, note that guidelines for body composition change based upon race and ethnicity, and different countries have different BMI guidelines. While BMI is a simple formula, BMI interpretation is best left to a qualified professional.
More on BMI
Want to compare a BMI to a range? Try the BMI Percentile Calculator which shows a body mass index compared to the distribution of BMIs for American adults.