What is BMI?
Body Mass Index (BMI) is a simple ratio of your weight to your height. It is calculated as weight in kilograms divided by height in metres squared. A person who is 70 kg and 1.70 m tall has a BMI of 70 / (1.70 × 1.70) = 24.2. Doctors and public-health bodies use it as a quick screening tool because it needs no equipment and works at population level.
BMI categories
The standard World Health Organization adult ranges are:
- Under 18.5 – underweight
- 18.5 to 24.9 – healthy weight
- 25 to 29.9 – overweight
- 30 and above – obesity
BMI for Indians and South Asians
South Asians tend to carry more body fat and more abdominal fat at the same BMI, so risk of type 2 diabetes and heart disease rises earlier. Many Indian guidelines therefore treat a BMI of 23 or higher as overweight and 25 or higher as obese. If you are of South Asian descent, read your result with these tighter cut-offs in mind.
Limits of BMI
BMI cannot tell muscle from fat. A muscular athlete can land in the "overweight" band with low body fat, while someone with little muscle can have a "normal" BMI and still carry too much fat. Use it alongside waist size and a body fat estimate rather than on its own. It is also not designed for children, pregnant women or people over 65 without a doctor's input.
Frequently asked questions
What is a healthy BMI?
For most adults a BMI between 18.5 and 24.9 is considered healthy under WHO guidelines. For South Asian adults, many guidelines use 18.5 to 22.9.
Is BMI accurate for athletes?
Not always. BMI does not separate muscle from fat, so muscular people can be labelled overweight. Body fat percentage and waist measurement give a better picture.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. Or switch the calculator above to imperial units.
Results are estimates for general information and are not medical advice. See our disclaimer. Talk to a doctor or registered dietitian before making major changes to your diet or training.