Calculate body mass index and see where you fall in the WHO weight categories.
Body Mass Index estimates body fat from your weight relative to height. It's a useful population screening tool but doesn't distinguish muscle from fat, so athletes may read high.
Metric — BMI = kg/m²
BMI = weight (kg) ÷ height (m)²
Imperial — BMI = 703 × lb / in²
BMI = 703 × weight (lb) ÷ height (in)²
Body Mass Index is weight divided by height squared. That is the whole of it. It was devised in the 1830s by Adolphe Quetelet as a way to describe populations, not to diagnose individuals, and it is still most reliable used that way.
The standard WHO categories are:
| Category | BMI |
|---|---|
| Underweight | below 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese class I | 30.0 – 34.9 |
| Obese class II | 35.0 – 39.9 |
| Obese class III | 40.0 and above |
BMI does not know what your weight is made of. That produces predictable errors:
low body fat. A rugby forward and a sedentary person of the same height and weight get the same BMI.
unchanged while body composition worsens.
under-reads very tall people and over-reads very short people.
Asian populations, and several health bodies use a lower overweight threshold of around 23 for these groups.
BMI is a screening signal, not a diagnosis. A number in the overweight band is
a reason to look further, not a conclusion on its own.
because it reflects abdominal fat specifically. Above roughly 94 cm for men and 80 cm for women, risk begins to rise.
height.
Track the trend rather than the single reading. A BMI moving steadily in one direction over months tells you something real; a reading that differs by 0.4 from last week tells you about hydration and what you last ate.
If you want a figure that drives actual decisions, the TDEE calculator and calorie calculator are more actionable, because they output something you can change.
This is an estimate and not medical advice. BMI is a screening tool, not a diagnostic measure. Consult a healthcare professional for health decisions.
BMI is a general screening measure. It can misclassify very muscular people and doesn't account for age, sex, or fat distribution. Treat it as a starting point, not a diagnosis.
The WHO considers 18.5–24.9 the normal range for most adults. Discuss your individual healthy weight with a healthcare provider.