Reference
NHS BMI Categories for Adults: UK BMI Ranges
The adult BMI categories used in the UK are underweight below 18.5, healthy weight 18.5 to 24.9, overweight 25 to 29.9, and obese 30 or above.
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This page gives the plain adult BMI category table behind the UK BMI calculator and the UK BMI chart. It is independent and not affiliated with the NHS, but it follows the adult category wording used by NHS public guidance.
Adult BMI categories for most UK adults
| BMI result | Adult category | What the boundary means |
|---|---|---|
| Below 18.5 | Underweight | Weight is low for height by the adult BMI scale. |
| 18.5 to 24.9 | Healthy weight | Lower-risk BMI range for most adults. |
| 25 to 29.9 | Overweight | Higher long-term risk, especially with a larger waist. |
| 30 and above | Obese | Stronger reason to speak to a GP or weight-management service. |
Lower BMI thresholds for some ethnic backgrounds
The NHS uses lower overweight and obesity thresholds for adults of Asian, Middle Eastern, Black African or African-Caribbean family background because weight-related health risks can rise at lower BMIs.
| Category | Most adults | Asian / Black / Middle Eastern adults |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Healthy weight | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25 to 29.9 | 23 to 27.4 |
| Obese | 30 and above | 27.5 and above |
Why the exact number matters
BMI categories are boundary-based. A BMI of 18.5 is healthy weight, not underweight. A BMI of 24.9 is still within the healthy range for most adults. A BMI of 25.0 is the start of overweight, and 30.0 is the start of obesity.
For a weight-by-height view, use the BMI chart UK. For your own number, use the BMI calculator UK.
When BMI categories need caution
- Children and teenagers use age- and sex-adjusted BMI centiles.
- Pregnancy is not assessed with adult BMI categories in the same way.
- Very muscular adults can be placed too high by BMI because muscle and fat are not separated.
- Older adults may need extra context around frailty, muscle loss and unintentional weight change.
Frequently asked questions
What are the NHS BMI categories for adults?
For most adults, below 18.5 is underweight, 18.5 to 24.9 is healthy weight, 25 to 29.9 is overweight, and 30 or above is obese.
Is 18.5 underweight or healthy?
A BMI of 18.5 is the lower edge of the healthy weight range for adults. Below 18.5 is underweight.
Is 25 overweight?
For most adults, yes. A BMI of 25.0 is the start of the overweight range. For some ethnic backgrounds, overweight starts at 23.
Is 30 obese?
For most adults, yes. A BMI of 30 or above is in the obese range. For some ethnic backgrounds, obesity starts at 27.5.
Do these categories apply to children?
No. Children and teenagers use BMI centiles, which compare their BMI with others of the same age and sex.
Calculate your BMI now
Use the free UK BMI calculator — instant, imperial or metric, and shows where you sit against the UK population.
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Not medical advice. If you have questions about your weight or health, speak to your GP. This site is not affiliated with the NHS.