What is BMI Calculator?
Work out your body mass index from your height and weight, in either metric or imperial units. Alongside the number you get your weight category and — more usefully — the actual weight range considered healthy for your height, so the result means something concrete.
How to use BMI Calculator
- Choose metric (cm/kg) or imperial (ft/lb) units.
- Enter your height.
- Enter your weight.
- Read your BMI, category and the healthy weight range for your height.
Why use this tool?
Shows your target range, not just a number
A BMI of 27 means little on its own. Seeing that a healthy range for your height is, say, 59–79 kg turns it into something you can act on.
Both unit systems
Switch between cm/kg and ft/lb without converting anything by hand — useful when forms and doctors use different units.
Frequently asked questions
What is a healthy BMI?
The World Health Organization considers 18.5–24.9 the normal range, under 18.5 underweight, 25–29.9 overweight, and 30 or above obese. These thresholds are population-level guidance rather than a personal diagnosis.
Is BMI accurate for everyone?
No, and this is worth being clear about. BMI cannot distinguish muscle from fat, so muscular athletes often register as “overweight” while being very healthy. It is also less reliable for children, older adults, pregnant people and some ethnic groups, where different thresholds may apply.
Should I change my diet based on this?
Treat BMI as a rough screening signal, not medical advice. Waist circumference, body composition, blood markers and fitness tell a far fuller story — talk to a doctor before making significant changes.
Is this tool really free?
Yes, completely free with no limits, no watermarks, no account and no trial period. Because everything runs on your own device, there are no server costs to pass on to you.