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BMI Calculator
Body mass index divides weight by the square of height to place a body somewhere on a single scale. It is a screening number used by health services for populations, not a diagnosis for a person. This calculator accepts centimetres and kilograms or inches and pounds.
How to use it
- Choose metric or imperial units.
- Enter your height and your weight.
- Read the index and the range it falls into.
Examples
- 170 cm, 68 kg → BMI 23.5, inside the 18.5–24.9 range.
- 5 ft 9 in (69 in), 185 lb → BMI 27.3, in the overweight band.
- Same weight, 10 cm taller: the index drops by roughly 2.5 points, because height is squared.
Questions people ask
Why does BMI mislabel muscular people?
The formula only knows two numbers and cannot tell muscle from fat. A dense, well-trained body weighs more for its height and often lands in the overweight band while being perfectly healthy. Waist measurement and body composition tell a fuller story.
Do children use the same ranges?
No. For anyone under 20, BMI is read against age-and-sex percentile charts rather than the fixed adult bands, because body composition changes throughout growth. Use the values here for adults only and ask a doctor about a child's chart.
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Updated: 2026-08-07