Body metrics · calculator
BMI calculator
Your body mass index relates weight to height. It is a quick screen — combine it with your waist size for a better picture.
Results are calculated in your browser and nothing you enter is stored.
BMI categories for adults
| BMI | Category (CDC / WHO) |
|---|---|
| below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25.0–29.9 | Overweight |
| 30.0–34.9 | Obesity class 1 |
| 35.0–39.9 | Obesity class 2 |
| 40 and above | Obesity class 3 (severe) |
The formula: weight in kilograms divided by height in metres squared (or 703 × pounds ÷ inches²). For children and teens, BMI is compared with age- and sex-specific percentiles instead — this calculator is for adults.
When BMI misleads
- Muscular people can have a high BMI with little body fat.
- Older adults lose muscle; a "normal" BMI can hide too much fat.
- Asian ancestry: health risks rise at lower BMI. Many guidelines use 23 as the overweight and 27.5 as the obesity threshold, and the ADA recommends diabetes screening from a BMI of 23.
- Where fat sits matters more than how much. Belly fat is the risky kind — check your waist-to-height ratio as well.
Weight and blood pressure
Excess weight is one of the strongest drivers of high blood pressure. Losing weight lowers systolic pressure by roughly 1 mmHg per kilogram (2.2 lb) lost — and even 5% of body weight improves blood pressure, blood sugar and cholesterol. See lifestyle measures that lower blood pressure.
Screening tools give a first orientation, not a diagnosis. Talk to your doctor about your results, especially before major changes to diet, exercise or medication.