What is a healthy BMI according to WHO?

According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered normal weight. Under 18.5 is underweight. 25–29.9 is overweight. 30 or above is obese. These thresholds apply in the United States, Europe, Australia, and most of the world.

What BMI is considered obese in Japan?

In Japan, a BMI of 25 or above is classified as obese (肥満, Himan) by the Japan Society for the Study of Obesity (JASSO). This is significantly lower than the WHO obesity threshold of 30. A BMI of 26 is 'overweight' by WHO but 'obese grade 1' in Japan. This stricter standard is one reason Japan has one of the world's lowest official obesity rates.

Why are BMI standards different in Asian countries?

Research shows that at the same BMI, people of East and South Asian descent tend to have a higher percentage of body fat and develop metabolic conditions at lower BMI values than people of European descent. The Asia-Pacific guideline (WHO Regional Office for the Western Pacific) sets overweight at BMI ≥23 and obesity at ≥27.5, lower than the global WHO standards of ≥25 and ≥30.

How is BMI calculated?

BMI = weight (kg) ÷ height² (m²). In imperial units: BMI = (weight in lbs × 703) ÷ height in inches². The formula is the same worldwide — only the category thresholds differ between countries.

What is the BMI overweight threshold in China?

China uses the WGOC (Working Group on Obesity in China) standard: BMI ≥24 is overweight and BMI ≥28 is obese. This is stricter than WHO (overweight ≥25, obese ≥30) but less strict than Japan (obese ≥25).

Do UK doctors use a different BMI standard?

The UK NHS uses WHO BMI classifications (overweight ≥25, obese ≥30) for most patients. However, for South Asian, Black African, and Caribbean patients, the NHS recommends lower intervention thresholds — effectively applying Asia-Pacific standards (overweight ≥23, obese ≥27.5) to account for higher metabolic risk at lower BMI values.

What is a healthy BMI for a 5'9 adult?

At 5'9" (175.3 cm), a healthy BMI of 18.5–24.9 means a weight of approximately 125–169 lbs (57–77 kg) by WHO standards. Under Asia-Pacific guidelines, the normal range is 18.5–22.9, which is approximately 125–152 lbs (57–69 kg) at that height.

🌍 WHO Global 🌏 Asia-Pacific 🇯🇵 Japan JASSO 🇨🇳 China WGOC 🇬🇧 NHS UK

BMI Calculator

Q: Is BMI calculated differently for children?

Yes. For children and teens (ages 2–19), BMI is interpreted using age- and sex-specific growth charts, not fixed cut-off numbers. The same raw BMI value means different things at different ages. Adult BMI thresholds (18.5, 25, 30) do not apply to children.

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.

Quick Answer

WHO healthy BMI: 18.5–24.9. Japan (JASSO) classes BMI ≥25 as obese — what WHO calls "overweight". Asia-Pacific sets overweight at ≥23. China (WGOC) uses overweight ≥24, obese ≥28. A BMI of 26 is simultaneously: "overweight" (WHO), "obese grade 1" (Japan), "obese class I" (Asia-Pacific), and "overweight" (China).

Weight (kg)

Height (cm)

How BMI is Calculated

BMI = weight (kg) ÷ height² (m²)

In imperial: BMI = (weight in lbs × 703) ÷ height in inches². The formula is universal — every country uses the same arithmetic. What differs are the category boundaries (the cut-off numbers that define "overweight" or "obese").

BMI Standards by Country — Comparison Table

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 Japan Uses a Different BMI Standard

Japan's Japan Society for the Study of Obesity (JASSO) classifies BMI ≥25 as obese — a threshold 5 points lower than the WHO's obesity cutoff of 30. This is not an arbitrary choice:

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Body composition

At the same BMI, East Asian people typically have a higher percentage of body fat than people of European descent.

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Health risk evidence

Type 2 diabetes, hypertension, and metabolic syndrome appear at lower BMI values in East Asian populations — consistent across multiple large studies.

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Public health policy

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.

BMI Limitations

BMI is a population-level screening tool, not a clinical diagnosis. Known limitations:

Doesn't distinguish muscle from fat

A muscular athlete may have BMI 28 without excess body fat. Bodybuilders routinely score "obese" by BMI.

Doesn't measure fat distribution

Central (abdominal) fat is more metabolically dangerous than fat elsewhere. BMI doesn't capture this — waist circumference does.

Age differences

Older adults often have "normal" BMI but higher fat percentage due to muscle loss. Younger adults may be healthy at the same BMI.

Sex differences

Women naturally carry more body fat than men at the same BMI. Sex-specific BMI interpretations exist but aren't widely used clinically.

Frequently Asked Questions

What BMI is healthy for a 5'9" adult? ▾

At 5'9" (175 cm), a WHO-healthy BMI of 18.5–24.9 corresponds to roughly 125–169 lbs (57–77 kg). Under Asia-Pacific guidelines, the normal range (18.5–22.9) is 125–151 lbs (57–69 kg). The Japan JASSO "normal" range is the same as WHO at this height.

Is BMI calculated differently for children? ▾

Yes. For children and teens (2–19 years), BMI is interpreted using age- and sex-specific percentile charts, not fixed cut-offs. A child at the 85th percentile is "overweight" and 95th percentile is "obese" — regardless of the raw BMI number. Adult thresholds (18.5, 25, 30) do not apply to children.

Do UK doctors use the same BMI standard as the US? ▾

The NHS uses WHO standards (overweight ≥25, obese ≥30) for most patients. However, the NHS specifically recommends lower intervention thresholds for South Asian, Black African, and Caribbean patients: overweight ≥23, obese ≥27.5 — aligning with Asia-Pacific guidelines.

What BMI is considered healthy in South Korea? ▾

South Korea uses the Asia-Pacific standard: normal BMI is 18.5–22.9, overweight is 23.0–24.9, and obese is ≥25. Korean health checkups typically flag patients with BMI above 25 for lifestyle intervention, not 30 as in Western countries.

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BMI Calculator — All Countries

Each country page shows local obesity statistics, the BMI standard used by the national health authority, and country-specific FAQs.

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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.

Standards and figures reviewed 2026.