How to use the BMI Calculator
- Choose metric or imperial units.
- Enter weight and height.
- Read BMI, category and healthy range.
How it works
BMI = weight (kg) ÷ height (m)². Imperial: 703 × weight (lb) ÷ height (in)². WHO adult categories: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and above obesity.
Worked example
70 kg at 170 cm: 70 ÷ (1.70 × 1.70) = 24.2, in the normal range; the healthy range for that height is about 53.5–72 kg.
Good to know
BMI does not distinguish muscle from fat and varies with age, sex and ethnicity, so use it as one indicator only.
For children and teens, BMI is interpreted by age-and-sex percentiles, which this adult tool does not cover.
Speak to a health professional for personal advice.
Frequently asked questions
For adults, 18.5 to 24.9 according to the WHO.
Not always; muscular people can have a high BMI without excess fat.
Weight in kilograms divided by height in metres squared.
Results are estimates for information only and are not financial, tax or legal advice.