BMI Calculator
Check your Body Mass Index — a quick screening number based on height and weight.
Your results
What is BMI?
Body Mass Index is weight divided by height squared (kg/m²) — a screening number used worldwide to categorise weight status. This BMI calculator gives your score and category using the World Health Organization's cut-offs: under 18.5 is underweight, 18.5–24.9 healthy, 25–29.9 overweight, and 30+ obese.
How it works — and where it breaks
BMI = weight (kg) ÷ height (m)². Across whole populations it correlates well with health risk, which is why researchers and doctors use it. For individuals it has a famous blind spot: it cannot tell muscle from fat. A lean 90 kg lifter and a sedentary 90 kg office worker of the same height get the same score. Rugby players, sprinters and serious lifters routinely register "overweight" at single-digit body fat.
That's why we recommend pairing BMI with a body composition measure — our body fat calculator or waist-to-height ratio — before drawing any conclusions.
Frequently asked questions
Is BMI useless for athletes?
For classifying them, mostly yes. For tracking, it still moves in the right direction when you gain or lose — just pair it with waist or body fat measurements to know what you gained or lost.
Do BMI categories differ by ethnicity?
Yes — the WHO notes that health risks begin at lower BMIs in many Asian populations, where an action point of 23 rather than 25 is often used.
References
- World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894. 2000.
- WHO Expert Consultation. Appropriate body-mass index for Asian populations. Lancet. 2004;363(9403):157–163.
Related
These results are estimates for healthy adults and are not medical advice. Consult a health professional before making major changes to your diet or training.
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