BMI Calculator Body Mass Index
Work out your Body Mass Index in metric or imperial units, with category, healthy weight range and a visual scale.
Formula: BMI = weight (kg) / height (m) squared. Imperial inputs are converted at 1 kg = 2.20462 lb.
About BMI Calculator
Body Mass Index is a single number comparing your weight with your height — weight in kilograms divided by the square of height in metres. It is the screening tool used by the WHO and most national health services to sort adults into four bands: underweight below 18.5, healthy 18.5 to 24.9, overweight 25 to 29.9, and obese at 30 and above.
The healthy weight range shown alongside the result is simply the weight that puts your height at BMI 18.5 and BMI 24.9, so it is a quick way to read the same figure as a target interval. Remember what BMI cannot do: it does not distinguish muscle from fat, so it under-reads for athletes and older adults with low muscle mass, and it is not valid for children, teenagers or pregnant people — those need age- and sex-specific percentile charts.
- 100% free, no signup required
- Works entirely in your browser
- Your data never leaves your device
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