BMI Calculator

4 days ago
2 min read

About BMI

What Does My BMI Number Mean?

Body mass index (BMI) is a simple way to compare your weight to your height. It’s commonly used to estimate whether you’re in a healthy weight range.

For adults (age 20 and older), BMI falls into four main categories:

Below 18.5: Underweight
18.5 – 24.9: Healthy weight
25.0 – 29.9: Overweight
30.0 and above: Obesity

Some groups may face health risks at lower BMI levels. For example, people of Asian descent may be considered:

Overweight at a BMI of 23–25
Obese at a BMI of 25 or higher

BMI for Children and Teens

BMI is calculated differently for those under 20. Instead of fixed ranges, it uses percentiles based on age and sex:

Below 5th percentile: Underweight
5th to <85th percentile: Healthy weight
85th to <95th percentile: Overweight
95th percentile or higher: Obesity

This approach accounts for normal growth and differences between boys and girls.

What BMI Doesn’t Tell You

While BMI is a useful screening tool, it doesn’t directly measure body fat or overall health. Here are some key limitations:

Fat distribution: BMI doesn’t show where fat is stored. Fat around the organs (visceral fat) carries higher health risks than fat under the skin.
Age: Body fat tends to increase naturally after age 30.
Sex: At the same BMI, women typically have more body fat than men.
Race and ethnicity: Body composition can vary across different groups.
Muscle mass: Muscular individuals may have a high BMI but low body fat.
Pregnancy: BMI is not a reliable measure during pregnancy.

How to Use Your BMI

BMI can help identify whether your weight might increase your risk for certain health conditions. However, it should not be used on its own to judge your health.

It doesn’t determine if you are “healthy,” nor does it diagnose any condition. For a complete picture, it’s best to discuss your BMI along with other factors—like lifestyle, medical history, and body composition—with a healthcare provider.