Free Online BMI Calculator
BMI is a screening figure, not a diagnosis — the calculator shows the bands and their limits so you can read them correctly.
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How to use BMI Calculator
- Select metric or imperial.
- Enter height and weight.
- Read your BMI and the category range.
Questions about BMI Calculator
Is BMI accurate for athletes?
Poorly. Muscle weighs more than fat, so a lean, muscular person can be flagged as overweight.
Are children judged the same way?
No. Under 18 uses age and sex percentiles, so speak to a clinician instead of using this figure.
About BMI Calculator
Calculate your body mass index and weight range with our free online BMI Calculator. 100% browser-based, fast, and private—no login or file uploads required.
These calculators and converters turn everyday numbers into answers instantly: percentages, BMI, loans and interest, units, colours and dates, with the formula shown so you can check the working.
This tool runs in your browser. The file is not uploaded. Results update as you type and are rounded for display; for money or legal figures keep the unrounded value and double-check against your own spreadsheet before relying on it.