BMI Calculator

Body mass index (BMI) compares your weight with your height. Doctors and public health agencies use it as a quick first check, because a BMI far from the healthy range is linked with higher risk of conditions such as type 2 diabetes, heart disease and some cancers.

BMI does not measure body fat directly. It is a screening number: a useful starting point for a conversation with a health professional, not a diagnosis.

BMI = weight ÷ height²

weight

body weight in kilograms

height

height in metres

For pounds and inches the equivalent is 703 × weight (lb) ÷ height (in)².

• Below 18.5: underweight
• 18.5 to 24.9: healthy weight
• 25 to 29.9: overweight
• 30 or higher: obesity (30–34.9 class 1, 35–39.9 class 2, 40+ class 3)

• Muscular people can score as overweight without carrying excess fat.
• It does not show where fat is stored. Waist size adds useful information.
• Some health bodies use lower cut-offs for people of South Asian, Chinese and other Asian backgrounds, often 23 for increased risk and 27.5 for high risk.
• These adult ranges do not apply to children and teens, whose BMI is compared with growth charts for their age and sex. They also do not apply during pregnancy.

• World Health Organization: Obesity and overweight fact sheet
• CDC: Adult BMI categories