BMI calculator
Enter your height and weight to see your BMI, the band it falls in and the healthy weight range for your height. Switch to the lower scale if your family background is South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean.
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How BMI is worked out
BMI is your weight in kilograms divided by the square of your height in metres. Someone 1.75 m tall who weighs 80 kg has a BMI of 80 ÷ (1.75 × 1.75), which comes to 26.1. Enter pounds and inches and the calculator converts them first, using the exact definitions of both units.
The two scales
| Band | Standard (WHO) | Lower cut-offs |
|---|---|---|
| Underweight | under 18.5 | under 18.5 |
| Normal | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25 to 29.9 | 23 to 27.4 |
| Obese class I | 30 to 34.9 | 27.5 to 32.4 |
| Obese class II | 35 to 39.9 | 32.5 to 37.4 |
| Obese class III | 40 and above | 37.5 and above |
The standard scale is the World Health Organization’s, unchanged since its 2000 report. In 2004 a WHO expert consultation found that in many Asian populations the risk of diabetes and heart disease starts to climb at a lower BMI, and it proposed action points at 23, 27.5, 32.5 and 37.5. NICE’s 2025 obesity guideline now tells doctors in England to use 23 and 27.5 as the thresholds for overweight and obesity in people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, and to lower the two higher classes by the same 2.5.
What BMI leaves out
BMI cannot tell muscle from fat, or say where your fat sits. A rugby player and a sedentary office worker can share a number and very different health. That is why NICE asks for a waist measurement alongside it for adults with a BMI under 35, and our waist-to-height calculator takes a minute with a tape. For the full story, read BMI chart for adults, with the lower cut-offs.
Sources
- World Health Organization. Obesity: preventing and managing the global epidemic. Technical Report Series 894, 2000.
- WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet, 2004.
- NICE. Overweight and obesity management, guideline NG246, 2025. Recommendations 1.9.10 to 1.9.12.
These calculators give estimates for adults, not a diagnosis. Nothing you type leaves this page.