BMI Calculator
Body Mass Index is calculated the same way everywhere — but the thresholds that define "healthy" differ by country. Enter your measurements to see your BMI under four international standards at once.
Use this calculator if you want the same BMI arithmetic scored under WHO, Japan (JASSO), Asia-Pacific and China (WGOC) at once. Skip it if you are under 18, pregnant, or a high-muscle athlete — BMI is a population screen, not a diagnosis. WHO healthy BMI: 18.5–24.9. Japan classes BMI ≥25 as obese (WHO’s “overweight”). Asia-Pacific overweight starts at 23. A BMI of 26 is overweight (WHO), obese grade 1 (Japan), and obese class I (Asia-Pacific).
At a glance
WHO healthy
18.5–24.9
US, Europe, Australia default
Japan obese
BMI ≥ 25
JASSO — WHO still calls this overweight
Asia-Pacific overweight
BMI ≥ 23
WPRO / IASO; NHS uses this for some groups
China overweight
BMI ≥ 24
WGOC; obese at 28
Run a site? Embed this BMI calculator on your own pages — free, four standards, no signup.
How is BMI calculated?
BMI is weight in kilograms divided by height in metres squared. In imperial units it is pounds times 703, divided by height in inches squared. Every country on this page uses that same arithmetic — the only thing that changes is the labelled category, which is why a BMI of 26 can be overweight in the US and obese in Japan.
What BMI is obese in Japan versus WHO?
Japan’s JASSO guideline labels BMI 25 and above as obese. WHO labels 25–29.9 as overweight and 30+ as obese. Asia-Pacific (WPRO/IASO) starts overweight at 23 and obesity at 27.5. China (WGOC) uses overweight at 24 and obesity at 28. Check the table — the formula did not change; the public-health cut-off did. Sources: WHO 2000, WPRO/IASO 2000, JASSO 2011, WGOC 2004, reviewed June 2026.
| Category | 🌍 WHO / Global | 🌏 Asia-Pacific | 🇯🇵 Japan | 🇨🇳 China WGOC |
|---|---|---|---|---|
| Underweight | < 18.5 | < 18.5 | < 18.5 | < 18.5 |
| Normal weight | 18.5 – 24.9 | 18.5 – 22.9 | 18.5 – 24.9 | 18.5 – 23.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 27.4 | ≥ 25 = Obese | 24.0 – 27.9 |
| Obese / At risk | ≥ 30.0 | ≥ 27.5 | — (all ≥25 = obese) | ≥ 28.0 |
Sources: WHO 2000, WPRO/IASO/IOTF 2000, JASSO 2011, WGOC 2004.
Why does Japan use a different BMI standard?
JASSO set obesity at BMI 25 because East Asian populations tend to carry more body fat, and to develop type 2 diabetes and metabolic syndrome, at a lower BMI than European-descent populations. The lower cut-off is a clinical-risk choice, not a translation quirk. It is also why Japan’s official obesity rate looks low: the same body can be “overweight” in New York and “obese grade 1” in Tokyo.
At the same BMI, East Asian people typically have a higher percentage of body fat than people of European descent.
Type 2 diabetes, hypertension, and metabolic syndrome appear at lower BMI values in East Asian populations — consistent across multiple large studies.
Japan's stricter threshold triggers earlier preventative care. It contributes to Japan having one of the world's lowest obesity rates by their own measure.
Who should skip this BMI calculator?
Skip it if you are a child or teenager (ages 2–19 need percentile charts, not adult cut-offs), if you are pregnant, or if you have high muscle mass — BMI cannot tell fat from muscle. Use it as a first screen, then add waist circumference and a clinician. The UK NHS still uses WHO cut-offs for most adults but recommends Asia-Pacific-like intervention thresholds for some South Asian, Black African and Caribbean patients.
A muscular athlete may have BMI 28 without excess body fat. Bodybuilders routinely score "obese" by BMI.
Central (abdominal) fat is more metabolically dangerous than fat elsewhere. BMI doesn't capture this — waist circumference does.
Older adults often have "normal" BMI but higher fat percentage due to muscle loss. Younger adults may be healthy at the same BMI.
Women naturally carry more body fat than men at the same BMI. Sex-specific BMI interpretations exist but aren't widely used clinically.
Key takeaways
- WHO healthy BMI for most adults is 18.5–24.9. Japan (JASSO) classes BMI ≥25 as obese — the same body WHO still calls overweight.
- Asia-Pacific overweight starts at 23; China (WGOC) at 24; obesity at 27.5 (Asia-Pacific) and 28 (China).
- The formula never changes. Only the labelled category changes. That is why a BMI of 26 can mean opposite advice in New York and Tokyo.
- BMI Prime is BMI ÷ 25 (1.0 = WHO overweight line). The result also shows the healthy weight range for your height under WHO and Asia-Pacific cut-offs.
- Skip adult BMI cut-offs for children, pregnancy, and high-muscle athletes. Pair with waist circumference and a clinician.
FAQ
BMI questions, answered straight
What is a healthy BMI according to WHO? ▾
What BMI is considered obese in Japan? ▾
Why are BMI standards different in Asian countries? ▾
How is BMI calculated? ▾
What is the BMI overweight threshold in China? ▾
Do UK doctors use a different BMI standard? ▾
Is BMI calculated differently for children? ▾
What is a healthy BMI for a 5'9 adult? ▾
Who should skip this BMI calculator? ▾
What BMI is considered healthy in South Korea? ▾
What is BMI Prime? ▾
BMI calculator by country
Which country BMI pages are worth opening?
We keep translated and country-specific BMI pages that add local authority guidance. Thin English name-swap URLs redirect here so they cannot dilute the canonical tool.
Sources & Methodology
BMI is weight (kg) divided by height (m) squared. We use the WHO international cut-offs as the default and surface country-specific thresholds (e.g. the lower overweight cut-offs used across much of Asia) where national bodies differ.
- World Health Organization — Obesity and overweight (BMI classification)
- U.S. CDC — Assessing Your Weight (Adult BMI)
- UK NHS — Calculate your body mass index (BMI)
- Japan Society for the Study of Obesity (JASSO)
Standards and figures reviewed 2026.