Adult BMI Calculator
Enter your height and weight to work out your Body Mass Index (BMI) and see which CDC weight category it falls into.
BMI is your weight divided by the square of your height, used as a quick screening check on whether your weight sits in a range associated with better health outcomes. For adults aged 20 and over, the CDC classes a BMI of 18.5 to 24.9 as the healthy range, below 18.5 as underweight, 25.0 to 29.9 as overweight, and 30.0 or above as obesity. BMI is a screening measure only — it does not diagnose a medical condition and does not measure body fat.
Before you use this calculator
- This calculator is intended for adults aged 20 and over.
- BMI is a screening measure, not a diagnosis.
- BMI does not diagnose a medical condition and does not measure body fat directly.
- Please speak to a doctor or another appropriate healthcare professional about any personal health concerns.
Adult BMI calculator
Your height and weight are used only in your browser to work out the number — they are never sent to us or stored anywhere. Weight categories are published by the Centers for Disease Control and Prevention (CDC).
What is BMI?
Body Mass Index is a number calculated from your height and weight. It gives a quick, rough indication of whether your weight sits in a range associated with better or worse health outcomes across large populations. It is widely used because it needs only two easily measured numbers — not because it is precise about any one person.
BMI does not measure body fat, and it cannot tell the difference between muscle and fat. A very muscular person can have a high BMI while carrying little fat, and someone within the healthy range can still carry more body fat than is ideal for them. Age, sex, ethnicity and body composition all affect what a given BMI actually means for an individual.
How BMI is calculated
The calculator above does this for you, but the arithmetic itself is simple — it is the same in either set of units:
| Units | Formula |
|---|---|
| Metric | weight (kg) ÷ height (m)² |
| Imperial | 703 × weight (lb) ÷ height (in)² |
A person weighing 70 kg at 1.75 m tall has a BMI of about 22.9, which falls in the healthy range.
Understanding your BMI result
For adults aged 20 and over, the CDC groups BMI into these categories. They apply to men and women alike, and they are screening categories — a way of deciding whether a conversation is worth having, not a diagnosis of anything.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity | 30.0 and above |
Source: Centers for Disease Control and Prevention (CDC). These ranges apply to adults aged 20 and over; BMI for children and teenagers is read against age- and sex-specific growth percentiles instead.
What a result does and doesn’t tell you
A BMI outside the healthy range is a prompt to look further, not a conclusion. Two people with the same BMI can be in very different health, and plenty of things BMI ignores — blood pressure, blood sugar, cholesterol, fitness, sleep, where body fat sits — matter more to your actual risk than the number itself. If your result surprises or worries you, that is a good reason to talk to a doctor or registered dietitian, who can look at the fuller picture.
BMI is least reliable for people whose body composition differs from the average: very muscular people, older adults who have lost muscle mass, and anyone who is pregnant. If you are in one of those groups, a BMI figure on its own is particularly weak evidence about your health.
What to do next
Whatever your result, the useful next step is the same: look at the habits behind it rather than the number itself. Our health and nutrition articles cover everyday eating, activity and prevention, and the nutrition checker lets you look up what is actually in the foods you eat. For anything specific to your own health, please talk to a qualified professional.
Frequently asked questions about BMI
This is not medical advice
Healthy Meal Plate provides general health and nutrition information for education. This calculator does not diagnose, treat, cure or prevent any disease, and it is not a substitute for advice from a doctor or registered dietitian. Healthy Meal Plate is not affiliated with, and is not endorsed by, the CDC. Read our nutrition standards.
Looking for something else? See all free tools.