What Is BMI and How to Read Your Result
BMI is a quick way to check whether your weight is in a healthy range for your height. Here is what the number means — and its limits.
Body Mass Index, or BMI, is one of the most widely used health screening numbers in the world. It gives you a quick sense of whether your weight sits in a healthy range for your height — using nothing more than those two measurements.
How BMI is calculated
BMI is your weight in kilograms divided by your height in metres squared. You do not need to do the maths by hand: a BMI calculator does it instantly in both metric and imperial units and tells you your category.
What the categories mean
- Under 18.5 — underweight
- 18.5 – 24.9 — healthy weight
- 25 – 29.9 — overweight
- 30 and above — obese
These ranges are used by health organisations worldwide as a general guide for adults.
The limits of BMI
BMI is a screening tool, not a diagnosis. It does not distinguish between muscle and fat, so very muscular people (like athletes) can read as "overweight" while being perfectly healthy. It also does not account for age, sex or where fat is stored. Treat it as a starting point, not the final word.
What to do with your result
If your BMI falls outside the healthy range, it is worth a conversation with a doctor rather than a crash diet. Small, sustainable changes to food and activity move the number over time. And remember: a single measurement is just a snapshot — trends matter more than one reading.