Body Mass Index (BMI) Calculator
Calculate your Body Mass Index from weight and height and see where you land on the WHO scale. Works with metric or imperial units, entirely in your browser.
What Body Mass Index measures
Body Mass Index (BMI) estimates body fat from two numbers you already know: weight and height. The metric formula is weight in kilograms divided by height in meters squared; the imperial version is 703 × weight in pounds divided by height in inches squared. The BMI calculator above handles both systems — pick Metric (kg, cm) or Imperial (lb, in) and it converts behind the scenes, so both give the same result apart from tiny rounding differences.
The WHO categories
The World Health Organization groups adult BMI into four bands: below 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30 or above is obesity. The calculator shows your category alongside your number, so you can see exactly where you land — for example, 70 kg at 175 cm gives a BMI of about 22.9, comfortably in the normal range.
What BMI doesn't tell you
BMI is a screening measure, not a diagnosis. It cannot distinguish muscle from fat, so athletes and very muscular people can score as overweight without excess body fat. It also does not account for age, sex, pregnancy or bone density — children and teenagers use age-adjusted percentile charts instead of the adult bands. Treat the number as a starting point for a conversation, not a verdict.
General information only — not medical advice
This tool provides general information only and is not medical advice. If your BMI falls outside the normal range, or if you have questions about what it means for you, talk to a qualified healthcare professional. Your results are for your eyes only. And like every tool here, it runs entirely in your browser: your weight and height are never uploaded, stored or tracked. Looking for a different kind of math? Try our percent calculator.
Frequently asked questions
What is Body Mass Index?
Body Mass Index estimates body fat from weight and height: weight in kilograms divided by height in meters squared (metric), or 703 × weight in pounds divided by height in inches squared (imperial).
What are the WHO BMI categories?
Underweight is below 18.5, normal weight is 18.5–24.9, overweight is 25–29.9, and obesity is 30 and above.
Do metric and imperial units give the same BMI?
Yes, apart from tiny rounding differences — both use the same formula with converted units.
Is BMI accurate for athletes?
Not always. BMI cannot tell muscle from fat, so very muscular people may score as overweight without excess body fat. It also does not account for age, pregnancy or bone density.
Is this medical advice?
No. This tool provides general information only. Talk to a qualified healthcare professional about what your BMI means for you.
Is my data uploaded?
No. Everything is computed locally in your browser; nothing you enter leaves this page.
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