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Body mass index (BMI) is a health metric used to gauge a person’s weight category quickly, as it’s a simple calculation of body fat relative to weight and height.
While BMI has its limitations—and should not be the only metric considered when determining your weight class—it’s a fast and accessible tool that can help you better understand whether you carry excess body fat, which can put you at risk for health complications ranging from type 2 diabetes to high blood pressure.
Check out the Forbes Health BMI calculator below to see where you stand.
BMI Calculator
What Is BMI?
Body mass index, or BMI, is a quick and inexpensive measurement of your body fat in relation to your weight and height. It’s often used as a screening tool for weight class categories, but it’s only moderately correlated with direct measurements of body fat, according to the Centers for Disease Control and Prevention (CDC).
In fact, even if two people have the same BMI, their body fat percentages may differ because a high BMI can indicate not only high levels of body fat, but also high levels of lean body mass, which is composed of muscle and bone.
How to Calculate BMI
BMI is calculated by dividing your weight in pounds by the square of your height in inches, and then multiplying by a conversion factor of 703, according to the CDC. See the formula below for an example.
Weight = 150 pounds
Height = 5’5″ (65 inches)
BMI calculation: [150 ÷ (65)2] x 703 = 24.96
BMI Interpretations for Adults
Weight status categories based on BMI for adults ages 20 and up, regardless of age or sex, are as follows, according to the CDC:
BMI Interpretations for Children and Teens
While BMI is calculated the same way for both adults and children, it’s interpreted differently. Whereas BMI for adults isn’t dependent on age or sex, it is dependent on those factors for children and teenagers.
For children and teens, the weight category in which they fall is deduced from a percentile chart (the one we use in our calculator comes from data obtained from the World Health Organization and applies to those ages 5 to 19). The percentile chart compares the BMI of children and teens to others who are the same age and sex. For example, if children or teens fall in the 75th percentile, their BMI is greater than 75% of other people of the same age and sex.
After receiving the percentile value from the chart, you can find the assigned weight category based on the table below:
BMI Limitations
As noted above, BMI is considered an imperfect measurement of body fat, as it doesn’t measure body fat directly. Additionally, BMI charts don’t take age, gender, race and ethnicity into account (with the exception of age and sex for children and teens), which can also impact your body fat or muscle. Indeed, experts note other factors you should take into consideration when determining your weight category include the location of fat, total muscle mass, age and gender. When calculating your BMI, keep these limitations in mind.
Calorie Calculator to Maintain and Lose Weight
Frequently Asked Questions (FAQs)
How do you calculate BMI?
To calculate BMI, divide your weight in pounds by the square of your height in inches, and then multiply by a conversion factor of 703.
What does BMI stand for?
BMI stands for body mass index, and it’s a measurement of body fat in relation to your weight and height.
What BMI is obese?
Currently, the CDC classifies a BMI of 30.0 and above as obesity for adults ages 20 and older.
What should my BMI be?
A healthy BMI for adults ages 20 and up is between 18.5 and 24.9, according to the CDC. Keep in mind, though, the limitations outlined in this article, and talk to your doctor about any weight-related concerns.
