BMI Calculator
Calculate your Body Mass Index (BMI) and check weight categories.
BMI calculator (body mass index)
This BMI calculator estimates whether your weight is healthy from your weight and height. It returns a number and the matching category from the WHO. It’s general guidance, not a medical diagnosis.
The BMI formula
For example, 70 kg and 1.75 m: BMI = 70 / (1.75 × 1.75) = 70 / 3.0625 = 22.9, within the normal range.
BMI categories (WHO)
| Category | BMI (kg/m²) |
|---|---|
| Underweight | below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obese | 30 and over |
What BMI does and doesn’t capture
BMI relates weight to height, but it doesn’t tell muscle from fat or where fat sits. A very muscular athlete may read as "overweight" with no excess fat, while BMI can underestimate fat in older people. Waist circumference or body-fat percentage are useful complements.
Frequently asked questions
What is a healthy BMI? Between 18.5 and 24.9 in adults, according to the WHO.
Does it work for children? For children, BMI-for-age and sex (percentiles) is used, not these adult ranges.
Does BMI measure fat? Not directly; it’s an estimate from weight and height, useful as a population screen.