BMI calculator
Body mass index is a quick screening number that compares your weight against your height. It will not tell you whether you are healthy, but it is the measure most clinics start from, and it takes two inputs.
How to use the bmi calculator
- Pick metric or imperial units.
- Enter your height and weight.
- Read the index and the healthy weight range calculated for your height.
How it works
BMI is weight in kilograms divided by height in metres squared. The adult categories are the same worldwide: below 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or above obese. Some health bodies use lower thresholds for people of South Asian descent, where cardiometabolic risk appears at a lower index.
The formula has known blind spots. It cannot distinguish muscle from fat, so athletes often read as overweight, and it does not account for where fat is carried, which matters clinically. It is not designed for children, pregnancy, or for people over about 65, who are measured on different charts.
Common questions
Is BMI accurate for everyone?
No. It is a population screening tool. Waist measurement, body composition and blood markers tell a doctor far more about an individual.
What is a healthy BMI?
Between 18.5 and 24.9 for most adults. The healthy weight range shown converts that band back into kilograms or pounds for your height.
Should I act on this number?
Treat it as a prompt for a conversation rather than a diagnosis. A doctor can interpret it alongside everything else about you.