BMI Calculator
Body Mass Index is a quick screen for whether your weight is in a healthy range for your height. This version also offers the lower thresholds that health bodies recommend for Asian and several other populations, who face higher risk at a lower BMI.
How BMI is calculated
BMI = weight(kg) ÷ height(m)²
The standard categories are: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30+ obese. But these were derived largely from white European populations.
Why ethnicity-adjusted ranges exist
A large body of evidence shows that people of South Asian, Chinese and other Asian, Middle Eastern, Black African and African-Caribbean backgrounds develop diabetes and heart disease at a lower BMI than white Europeans, because they tend to carry more fat around the organs at the same weight. The WHO and the UK's NICE therefore recommend lower cut-offs for these groups: overweight from 23 and obesity from 27.5.23 Selecting your background applies those thresholds.
BMI's blind spots
BMI knows nothing about muscle, so it labels many athletes 'overweight', and it can miss dangerous belly fat in someone of 'healthy' weight. It's a useful first screen, not a verdict. Waist-to-height ratio catches what BMI misses.4
Common questions
Which ethnicity option should I choose?
If your family background is South Asian, East/Southeast Asian, Middle Eastern, Black African or African-Caribbean, use the adjusted option; guidelines apply lower thresholds for these groups. Otherwise use standard.
Is BMI accurate for athletes?
Not very. Muscle weighs more than fat, so muscular people often register as 'overweight' by BMI while carrying little fat. Use a body-fat or waist measurement instead.
Is a low BMI always healthy?
No. Below 18.5 carries its own risks, and BMI can't tell muscle from fat. Someone with low muscle can be 'healthy' by BMI but still carry excess belly fat.
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Build my free planSources
- WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157-163. Source
- National Institute for Health and Care Excellence. Overweight and obesity management. NICE guideline NG246. Published January 2025. Source
- Ashwell M, Gunn P, Gibson S. Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis. Obes Rev. 2012;13(3):275-286. Source
This calculator is general information, not medical advice, and its results are estimates for healthy adults. Speak to a doctor or registered dietitian before making significant changes, especially if you are pregnant or breastfeeding, under 18, or manage a medical condition.
