BMI Calculator
Enter your height and weight to get your BMI and the category it falls into. Nothing is sent anywhere, the whole thing runs in your browser.
Your measurements
Fill in both fields and your BMI appears here.
What the number means
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity, class 1 |
| 35.0 to 39.9 | Obesity, class 2 |
| 40.0 and above | Obesity, class 3 |
These are the adult cut-offs used by the World Health Organization and the CDC. They do not apply to children, to pregnancy, or to anyone under 18.
BMI is a screening number, not a diagnosis
It compares your weight to your height and nothing else. It cannot tell muscle from fat, so it reads high for a lot of athletes and can read normal for someone carrying very little muscle. It says nothing about where fat sits on the body, which is the part most tied to health risk. And the standard cut-offs were drawn largely from European populations: the WHO notes that risk starts to rise at a lower BMI in many Asian populations, often quoted as 23 rather than 25. Treat it as one rough signal and let a clinician put it in context.
Where BMI gets used anyway
Whatever its flaws, BMI is the number written into most prescribing rules. The FDA labels for the approved weight-loss medicines set the bar at a BMI of 30 or more, or 27 or more alongside a weight-related condition such as high blood pressure, type 2 diabetes or sleep apnoea. Most insurers and telehealth programmes use the same two thresholds.
So the number matters practically even where it describes you poorly. If you are near a threshold, that is worth raising with a clinician rather than deciding either way from this page.
Frequently asked questions
How is BMI worked out?
Your weight in kilograms divided by your height in metres squared. In pounds and inches it is your weight multiplied by 703, divided by your height in inches squared. Both give the same answer.
Is a BMI of 25 bad?
It is the start of the overweight band, but a single number just over a line is not meaningful on its own. What usually matters more is the direction it is moving, your waist measurement, and your blood pressure and blood sugar.
Why does my BMI look high when I lift weights?
Because muscle is denser than fat and BMI cannot tell them apart. A muscular person often lands in the overweight or obese band while carrying very little body fat. This is the single most common way BMI misreads someone.
Does this work for children?
No. Children and teenagers are scored against age and sex percentile charts, not these fixed cut-offs. Ask a paediatrician instead of using this.
Is anything I type here stored?
No. The maths runs in your browser. Nothing is sent to a server and nothing is saved.
Category thresholds from the World Health Organization and the US Centers for Disease Control and Prevention. This tool is general information, not medical advice, and it cannot diagnose anything. Talk to a clinician about your own health.