Check your Body Mass Index (BMI) easily.
Body Mass Index is simply your weight in kilograms divided by your height in metres squared. It is a quick screening figure that sorts most adults into broad categories, and the standard ranges are:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
This is the part most calculators leave out, and it matters. BMI measures weight against height — it does not know the difference between muscle and fat. A lean, muscular athlete can register as "overweight" while carrying very little fat, and BMI can equally miss unhealthy fat levels in someone with low muscle mass. It also says nothing about where fat sits, even though waist fat carries more health risk. BMI is a useful, free first glance at a population level; it is not a diagnosis. For anything that affects decisions, treat the number as a prompt to talk to a doctor, who can factor in body composition, waist measurement, age, and ethnicity.
Is BMI accurate for athletes?
Often not. Muscle weighs more than fat, so very muscular people can land in the "overweight" range despite being lean and fit. Body-fat measurement is more meaningful for them.
Does BMI work for children?
Not with these adult ranges. Children and teens use age- and sex-specific percentile charts instead, so use a paediatric tool for under-18s.
What should I do with my result?
Use it as a rough check, not a target. If it sits well outside the healthy range and you are concerned, a doctor can interpret it alongside other measurements.
Is my data private?
Yes — the calculation runs in your browser and nothing you enter is uploaded or stored.