BMI Calculator
Body mass index in metric or imperial
BMI is a population screening statistic, not a diagnosis. It cannot tell muscle from fat, ignores bone density, body shape and visceral fat, and its thresholds shift with ethnicity-specific body composition. It is not intended for people under 18, pregnant people, or those with an eating disorder. Do not change your weight or diet based on this number alone — talk to a clinician or registered dietitian.
The arithmetic is one line: BMI = kilograms ÷ (metres × metres). Pick metric or imperial, type a weight and a height, and you get the index to one decimal place, the WHO category it lands in, and the weight range for your height that sits between 18.5 and 24.9. Imperial entries are converted internally — pounds at 0.453592 to the kilogram, inches at 0.0254 to the metre — and the normal-range band is shown in both units at once. The categories used here are the WHO adult cut-offs: under 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, 30 and above obesity. Those are population cut-offs, not targets for an individual, and the number says nothing about where on the body the weight sits.
Calculate your Body Mass Index with metric or imperial units and see which WHO weight category you fall into, with healthy-range guidance. Your data never leaves the browser.
Private BMI Calculator In Your Browser
BMI Calculator is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.
How to use BMI Calculator
Set the Units selector to Metric (kg, cm) or Imperial (lbs, in).
Enter your weight in the Weight field and your height in the Height field.
Read the BMI to one decimal place along with its WHO category.
Compare the healthy weight range against your Weight entry — it is given in both kilograms and pounds in imperial mode.
- Imperial entry is converted internally — pounds at 0.453592 to the kilogram, inches at 0.0254 to the metre — so no rounded intermediate figure is fed into the division.
- The healthy-weight band is derived from your own height by multiplying it by the 18.5 and 24.9 bounds, so it adapts rather than being a fixed table.
- Entering imperial units shows the range in pounds and kilograms side by side, which saves a second conversion.
- A zero or negative weight or height suppresses the results instead of printing a meaningless index.
- A nurse triages a patient's chart quickly at the start of an appointment and notes the index alongside the blood pressure reading.
- An adult joining a gym asks what weight range corresponds to their height before setting a target.
- A parent checking a growth chart for a school form looks up the same cut-offs the clinic uses.