Free BMI Calculator
Body Mass Index (BMI) is weight in kilograms divided by height in metres squared. It is a screening number that compares your weight to your height — not a diagnosis, and not a measure of body fat, muscle, or health on its own. Enter your height and weight below to get your BMI and category, with the WHO bands explained.
What is the BMI Calculator?
The BMI Calculator is a free tool that divides your weight by your height squared. It gives your BMI and category using WHO bands. It is a screening number, not a diagnosis. It does not measure body fat, muscle, or health on its own.
How to use this tool
- Choose your height unit — centimetres or feet and inches.
- Enter your height and your weight.
- Select Calculate my BMI to see your BMI.
- Read your category and the explanation beside it.
Your BMI
No sign-up needed — the tool works right here in your browser.
What the number means
- Underweight: BMI below 18.5
- Healthy range: BMI 18.5–24.9
- Overweight: BMI 25–29.9
- Obese: BMI 30 or above
These are the WHO cutoffs used worldwide. They describe populations, not individuals — a single number cannot tell you whether you are healthy.
What BMI cannot tell you
BMI does not measure body fat, muscle, bone density, or where fat sits on your body. A muscular person can land in the "overweight" band with very little body fat. An older adult can land in the "healthy" band while carrying more fat than is ideal. That is why BMI is best used as a starting point for a conversation with a clinician — not as a verdict on your body, and never as a reason to chase extreme goals.
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See plans & free trial →Frequently asked questions
What is a healthy BMI?
The WHO classifies BMI 18.5–24.9 as the healthy range for most adults. It is a population-level screening band, not a personal prescription — muscle, bone density, and body composition all affect what a healthy weight means for you.
Is BMI accurate?
BMI is a rough screening number. It does not measure body fat, muscle, or bone density, so athletic people can score as overweight while carrying little fat, and older adults can score healthy while carrying more fat. Treat it as one data point, not a verdict.
Does BMI work for everyone?
No. BMI cutoffs were developed for adults and are less meaningful for children, teenagers, pregnant people, and very muscular people. For personal guidance, talk to a clinician who can look at more than one number.
Do I need to sign up to use this BMI calculator?
No. The tool works right here in your browser — no account, no name or email needed.
Disclaimer: BMI is a general screening number, not a diagnosis. It does not account for muscle, bone density, or body composition. Not medical advice — talk to a clinician for personal guidance. This tool never recommends a target weight or extreme goals.