The adult BMI ranges
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Normal range |
| 25.0–29.9 | Overweight |
| 30.0–34.9 | Obesity class I |
| 35.0–39.9 | Obesity class II |
| 40.0+ | Obesity class III |
Calculate the number with the adult BMI calculator.
What “screening category” means
A screening measure helps identify who may benefit from additional context or assessment. It does not confirm a disease. A BMI category should be considered alongside blood pressure, laboratory results, waist size, activity, family history, and other clinical information.
A boundary does not create a sudden biological change
A BMI of 24.9 and 25.0 fall in different labels, but the 0.1 difference does not create an immediate health change. Categories are administrative and screening boundaries placed on a continuous number.
The same category can describe different bodies
A strength athlete and a sedentary adult may share the same “overweight” BMI while having different muscle, waist size, fitness, and health markers. Likewise, adults in the normal range can have very different risk profiles.
Why children use different interpretation
Children and teenagers are still growing, so BMI is interpreted using age- and sex-specific percentiles. Adult categories should not be applied to anyone under 18.
What to do with a result
First verify the inputs and units. Then consider context rather than reacting to the label alone. The BMI limitations guide and waist-to-height calculator explain useful next questions.
Frequently asked questions
Does BMI 30 automatically diagnose obesity?
BMI 30 enters the obesity screening range, but diagnosis and individual risk assessment require clinical context.
Why is 25 considered overweight?
It is a standardized population-screening boundary, not a point where health suddenly changes.
Are BMI categories the same for every adult?
The standard ranges are broadly applied, but individual interpretation can differ with age, build, pregnancy status, and clinical context.
Do older adults use a different formula?
The arithmetic is the same, but loss of muscle and other age-related changes can make interpretation more complicated.
Sources
References and further reading
Last reviewed: July 13, 2026