What BMI Calculator is
Metric uses centimetres and kilograms. Imperial uses feet, inches, and pounds. Switch the unit mode and the numbers you already typed convert in place. You do not re-enter height from scratch. BMI updates as you type. When the inputs are valid, the page also shows a healthy weight range for that height.
Categories follow the WHO adult table for people 20 and over. Underweight is below 18.5. Healthy is 18.5–24.9. Overweight is 25–29.9. Obese is 30 and above. Those four bands are the only scale this tool uses. It does not apply child or teen charts. It does not adjust for muscle mass, pregnancy, or frame. A high BMI can be muscle. A “healthy” BMI can still hide other risk. Treat the figure as a screening number, not a diagnosis and not medical advice. If you are under 20, pregnant, or an athlete with high lean mass, do not use this page as a verdict.
How to use it
- Pick metric or imperial. The other pane stays in sync when you switch.
- Enter height and weight. Imperial height is feet plus inches.
- Read the BMI, the WHO category, and the healthy weight range.
- Copy the result if you want a line in a note. Nothing else is saved.
Common uses
Get a quick adult BMI before a form that asks for it. See whether a weight sits in the 18.5–24.9 band for a given height. Compare metric clinic numbers with a stone-and-pound home scale by switching units. Designers and writers use it when a script needs a plausible adult range, not a clinical opinion. People use it after a weigh-in to see the category chip move. None of that replaces a clinician. The healthy weight range is the weight band that would land BMI between 18.5 and 24.9 at the height you entered. It is not a target you must hit.
The live convert on switch is there so you can check a tape in cm against a stone scale without a second tool. Rounding still applies. A converted pound figure may sit a gram off the metric original. That is expected. The WHO rows on the page highlight as the number crosses 18.5, 25, and 30. They do not add extra bands such as “obese class II.”
Privacy
Height and weight are not uploaded. We do not log the numbers. Refresh the page and the form is blank. We never see what you copy.