How to use the BMI calculator

1. Choose Metric or Imperial units.
2. Enter your height and weight.
3. Click Calculate BMI to see your index, category, and healthy weight range.

What is BMI?

Body Mass Index is weight in kilograms divided by height in metres squared. It is a screening measure used worldwide to categorise weight status: under 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, and 30 or above is obese.

Example

A person who is 170 cm tall and weighs 70 kg has a BMI of 24.2 — in the normal range. Their healthy weight range for that height is roughly 53.5–72 kg.

Limitations to keep in mind

BMI does not distinguish muscle from fat, so athletes may read as overweight despite low body fat. It is also less accurate for children, older adults, and pregnant women. Treat it as a starting point, not a diagnosis — talk to a health professional for personal advice.

Frequently asked questions

What is a good BMI? Between 18.5 and 24.9 for most adults.
Is BMI accurate? It is a useful population-level screening tool, but it does not measure body fat directly.
Does age affect BMI? The standard categories apply to adults 20 and over; children use age-and-sex percentiles instead.