Body Mass Index (BMI) Calculator

Clinical context

Body mass index (BMI) is an internationally recognised standard to classify the body weight of adults. Although BMI is not a perfect measure, it is the most useful and valid for adults. BMI is not an appropriate measure for children. If you are worried about your child’s weight, speak to your doctor. BMI formula for calculation: weight (kg) / (height (m) x height (m)). There are some exceptions – the healthy weight BMI range is generally: • lower for people of Asian background • higher for people of Polynesian background • higher for older people • higher for elite athletes with higher levels of lean body tissue • higher for pregnant women As the BMI calculation doesn’t take fat or muscle into account, you should measure your waist as well to get the full picture. Meaning of BMI ranges: • Less than 18.5 – Underweight • 18.5 to 24.9 – Healthy weight • 25 to 29.9 – Overweight but not obese • 30 to 34.9 – Obese class I • 35 to 39.9 – Obese class II • 40 or more – Obese class III