Free tool

BMI calculator

Find your body mass index in a few seconds.

Your BMI

Enter your height and weight.

<18.5Under 18.518.5–24.918.5–24.925–29.925–29.930+30+

What is BMI?

Body mass index, or BMI, compares your weight to your height. It’s a quick way to see if your weight falls in a range linked with higher health risks.

It’s a screening number, not a diagnosis. Clinicians look at it alongside your health history, labs, and how you feel day to day.

How it’s calculated

US units

weight (lb) ÷ height (in)² × 703

Example: 189 lb at 5′5″ = 31.4

Metric

weight (kg) ÷ height (m)²

Example: 86 kg at 1.65 m = 31.6

What the numbers mean

Adults 20 and older. Not for children, teens, or pregnancy.

UnderweightUnder 18.5

Can point to low nutrition or another health issue.

Healthy weight18.5–24.9

Linked with the lowest risk of weight-related conditions.

Overweight25–29.9

Higher chance of high blood pressure and type 2 diabetes.

Obesity, class 130–34.9

Risk of diabetes, heart disease, and sleep apnea goes up.

Obesity, class 235–39.9

Higher risk again, with more strain on joints and the liver.

Obesity, class 340 and up

The highest risk of serious long-term conditions.

What BMI doesn’t show

Muscle vs. fat

A very muscular person can have a high BMI and little body fat.

Where weight sits

Weight around the belly carries more risk. A waist measurement adds context.

Age, sex, and background

The same BMI can mean different things for different people.

BMI and GLP-1 medications

BMI is one of the things a clinician looks at. GLP-1 medications for weight are usually for adults with:

A BMI of 30 or more
A BMI of 27 or more, plus a condition like high blood pressure

These criteria come from FDA-approved GLP-1 medications for weight management. Compounded medications are not FDA-approved. A licensed clinician decides if treatment is right for you.

See if you qualify

BMI questions

Not always. Muscle weighs more than fat, so very fit people can land in a higher range. A waist measurement or body composition test gives a clearer picture.

No. Adults use the same ranges. At the same BMI, women tend to carry more body fat than men, so your clinician reads the number alongside the rest of your health.

Not with these ranges. For anyone under 20, BMI is compared with others of the same age and sex on a growth chart. A pediatrician can walk you through it.

Every few months is plenty for most adults. If you’re working on your weight, checking once a month can help you see progress without fixating on daily swings.