What this BMI calculator does
Enter your height and weight — in metric or imperial units — and this tool instantly shows your body mass index (BMI), your WHO weight category and the healthy weight range for your height. A scale shows where your value sits, from underweight through to obesity. Everything is calculated locally in your browser.
How BMI works
BMI is a simple ratio: your weight in kilograms divided by the square of your height in metres. It was designed as a quick way to screen large populations, not to diagnose any individual. The World Health Organization uses these bands:
| BMI | Category |
|---|---|
| under 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity (class I) |
| 35 – 39.9 | Obesity (class II) |
| 40 and above | Obesity (class III) |
Your healthy weight range
For your height, the calculator shows the weight range that corresponds to a BMI between 18.5 and 24.9. It is a useful reference point, but “healthy” is a range, not a single number — and where you should sit within it depends on your build, muscle mass and overall health.
What BMI does not tell you
BMI is quick but blunt. It cannot tell muscle from fat, so athletes and very muscular people often score as “overweight” despite being lean. It is also less reliable for:
- children and teenagers, who need age- and sex-specific percentile charts;
- older adults, whose muscle mass and height change;
- pregnant people;
- some ethnic groups, for whom health risks rise at different BMI thresholds.
For a fuller picture, waist circumference, body-fat percentage and a conversation with a doctor matter more than BMI alone.
Privacy
Your height and weight never leave your device. The calculation runs entirely in your browser and your inputs are only stored locally so the tool remembers them next time.
This calculator is for general information only and is not medical advice. Consult a healthcare professional for guidance about your weight and health.