BMI Calculator
Calculate Body Mass Index from height and weight, with standard WHO category ranges.
How this tool works
Enter your height
Toggle between centimeters or feet and inches.
Enter your weight
Toggle between kilograms or pounds - units can be mixed freely.
BMI calculates automatically
The standard formula runs immediately with no calculate button.
See the WHO category
Underweight, normal, overweight, or obese, alongside a clear screening-only disclaimer.
Quick facts
- Category
- Calculators
- Best for
- Getting a quick general health screening number
About this tool
Enter height (in centimeters or feet and inches) and weight (in kilograms or pounds) to calculate Body Mass Index and see which of the four standard World Health Organization categories it falls into: underweight (below 18.5), normal weight (18.5-24.9), overweight (25-29.9), or obese (30 and above). BMI is calculated the standard way - weight in kilograms divided by height in meters squared - with unit conversions handled automatically so you can mix imperial height with metric weight or vice versa. This tool is explicitly a general population screening measure, not a diagnostic health assessment: BMI doesn’t distinguish muscle mass from fat mass, doesn’t account for age, sex, or body composition, and an athlete with high muscle mass can show an "overweight" BMI despite having low body fat. Always consult a healthcare professional for individual health guidance. Runs entirely client-side.
Why use this tool
Mixed unit support
Use metric height with imperial weight, or any combination, without manual conversion first.
Standard WHO categories
Results map to the four widely used World Health Organization BMI ranges.
Honest about its limits
Clearly states this is a general screening measure, not a diagnostic health assessment.
Instant, live calculation
No calculate button - the result updates as soon as height and weight are entered.
Frequently asked questions
No - BMI is a population-level screening tool that only considers height and weight, so it can’t distinguish between muscle mass and fat mass, doesn’t account for age, sex, or body frame, and can misclassify very muscular people as overweight or obese despite low body fat. It’s useful as a rough, quick indicator across large populations, but it should never replace an actual health assessment from a qualified professional who can consider your individual circumstances.
The 18.5, 25, and 30 thresholds come from World Health Organization guidelines based on population studies correlating BMI ranges with health outcomes across large groups. They’re widely used as a standardized reference point specifically because they’re simple and consistent across studies, even though - as with any population-derived cutoff - they don’t perfectly apply to every individual.
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