Body Mass Index Calculator
Enter your height and weight to calculate your body mass index. The result is interpreted according to the World Health Organization classification.
This result is not a diagnosis
Body mass index is a screening measure based only on height and weight; it does not account for muscle mass, fat distribution, age or coexisting conditions, and can be misleading in athletes and older adults. Treatment decisions are made only after examination, investigation and clinical assessment.
How to Read the Result
Body mass index is a screening measure, not a diagnostic tool. A high value alone does not mean treatment is needed, and a normal value does not guarantee everything is fine. Where fat accumulates — particularly around the abdomen — can be as decisive for metabolic risk as BMI itself, sometimes more so.
Where bariatric surgery is concerned, guidelines start with body mass index, but the decision does not rest on that number alone: coexisting conditions, previous weight-loss attempts, eating behaviour and the ability to sustain long-term follow-up are assessed together.
Frequently Asked Questions
How is body mass index calculated?
Weight in kilograms divided by height in metres squared. For 80 kg and 1.75 m: 80 / (1.75 × 1.75) = 26.1.
What is a healthy BMI?
The World Health Organization defines 18.5–24.9 as normal. 25–29.9 is classified as overweight and 30 and above as obesity.
What BMI is required for bariatric surgery?
Guidelines consider 40 and above eligible for surgical assessment without requiring an associated condition. Between 35 and 40, assessment is made where a condition such as type 2 diabetes, hypertension or sleep apnoea is present. These are thresholds for assessment, not a decision to operate.
Can BMI be misleading?
Yes. BMI uses only height and weight; it does not account for muscle mass, fat distribution or age. It reads high in muscular people who train regularly and low in older adults who have lost muscle.