What is it?
The BMI Calculator works out your Body Mass Index, its Category, and the Healthy weight for your height.
Who is it for?
Adults checking whether their weight is in a healthy range, people starting a fitness plan, and anyone filling health forms that ask for BMI.
How to use it
- Choose Units: Metric (kg, cm) or Imperial (lb, ft, in).
- Enter your weight and height.
- Tick Use the cut-offs for South and East Asian people (WHO Asia) if that applies to you.
Categories
- Standard: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30+ obese.
- WHO Asia (tick the box): overweight from 23 and obese from 25, because health risks like diabetes and heart disease rise at lower BMI in Asian populations.
What BMI can’t tell
BMI is a quick screening number, not a diagnosis. It does not tell muscle from fat; children and teens need age-based BMI charts.
- Athletes may show “overweight” while being very fit.
- Older people may show “healthy” while having little muscle.
- Where fat sits matters: a large waist is riskier. Check your Waist-to-Hip Ratio or body fat too.
This is general information to help you understand your numbers, not medical advice. Talk to a doctor about your own health.
Worked example
70 kg and 170 cm: BMI = 70 ÷ (1.7 × 1.7) = 24.2, healthy on the standard scale, but overweight on the WHO Asia scale (23 and above).
Errors and how to fix them
- “Enter your weight (more than 0)” or “Enter your height (more than 0)”: a box is empty or 0.
- The BMI looks impossible (for example 3 or 300): the height is probably in the wrong unit. In Metric, type height in centimetres (170), not metres (1.70). In Imperial, type feet and inches in their own boxes.
Open the tool: BMI Calculator
Still stuck?
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Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.