Calculate your Body Mass Index in metric or imperial units and see your weight category instantly.
Anyone checking whether their weight is in a healthy range for their height.
Choose your units
Switch between metric (cm, kg) and imperial (ft/in, lb) — whichever you have your measurements in.
Enter height and weight
Type your measurements into the fields; there is no need to convert anything yourself.
Read your category
Your BMI and weight category appear instantly, colour-coded against the WHO ranges.
Body Mass Index is the quick screening number health services worldwide use to flag whether someone’s weight may be too low or too high for their height. It is simple in principle — weight divided by height squared — but easy to get wrong in practice, because the formula differs between metric and imperial and people routinely mix units or misremember the multiplier. Getting an accurate figure matters when a form, a doctor, or your own tracking asks for it. This calculator handles both metric (cm, kg) and imperial (ft/in, lb) correctly, so you never have to convert by hand, and it shows your result colour-coded against the official WHO categories the moment you enter your measurements. It runs entirely in your browser, so nothing you type is stored or uploaded. One important caveat built into how you should read the result: BMI is a screening tool, not a diagnosis — it does not distinguish muscle from fat, so use it as one reference point alongside other measures and professional advice.
Health check-ins
See whether your weight sits in the healthy range and track the trend over time.
Fitness goals
Use BMI as one reference point alongside body measurements when setting targets.
Medical & insurance forms
Compute BMI quickly whenever a form, doctor, or application asks for it.
Unit conversion
Get a correct BMI even when your height and weight are in different systems.
Parents & carers
Check an adult household member’s BMI without needing to remember the formula.
The WHO ranges are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30+ obese.
Metric: weight (kg) ÷ height (m)². Imperial: 703 × weight (lb) ÷ height (in)². This tool applies the right formula for your chosen units.
No — it is a screening tool, not a diagnosis. It does not separate muscle from fat, so very muscular people can read high and it is less reliable for the very tall or short.
Adult BMI categories do not apply to children and teens, who use age- and sex-specific percentile charts instead. Use this for adults.
Either — pick whichever matches your measurements. The result is the same once converted correctly.
Treat it as a starting point. For personalised advice, discuss it with a healthcare professional who can consider your full picture.
No. The calculation runs entirely in your browser; nothing is saved or uploaded.
Yes — it is completely free with no sign-up, in both metric and imperial units.