BMI Categories by Country
The body mass index is calculated the same way everywhere, but the line between "normal" and "overweight" is not. A BMI of 24 is normal under the WHO classes, overweight in China and pre-obesity in Korea. This guide shows the official tables side by side.
How BMI Is Calculated
BMI is weight in kilograms divided by height in metres squared: BMI = kg ÷ m². For 65 kg and 1.70 m, that is 65 ÷ 2.89 = 22.5. In pounds and inches, the US CDC gives the same result as weight ÷ height² × 703. The classes below apply to adults; children and teenagers are assessed with growth charts by age and sex, and BMI is not used to judge weight in pregnancy.
The International Classes
The WHO defines adult underweight as a BMI under 18.5, overweight as 25 or more and obesity as 30 or more. The US CDC uses the same limits for adults aged 20 and over and divides obesity into three classes:
| BMI | Class (CDC) |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to below 25 | Healthy weight |
| 25 to below 30 | Overweight |
| 30 to below 35 | Class 1 obesity |
| 35 to below 40 | Class 2 obesity |
| 40 or more | Class 3 obesity (severe obesity) |
The UK's NICE guideline NG246 uses the same thresholds for most adults (recommendation 1.9.10).
Lower Thresholds in Asia and for Some Groups
NICE recommends lower thresholds for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, because they are prone to central fat and their cardiometabolic risk occurs at a lower BMI: overweight from 23, obesity from 27.5, and obesity classes 2 and 3 usually 2.5 points lower than the general thresholds (recommendation 1.9.11). Several Asian countries set their own national standards:
| Standard | Normal | Overweight or pre-obesity | Obesity |
|---|---|---|---|
| WHO / US CDC | 18.5–24.9 | 25–29.9 | 30 and over (classes from 30, 35, 40) |
| UK NICE, some ethnic groups | 18.5–22.9 | 23–27.4 | 27.5 and over (32.5, 37.5) |
| Korea (KDCA; Korean Society for the Study of Obesity) | 18.5–22.9 | 23–24.9 (비만 전단계) | 25 and over (stages from 25, 30, 35) |
| Japan (MHLW; Japan Society for the Study of Obesity) | 18.5–24.9 | – | 25 and over (degrees from 25, 30, 35, 40) |
| China (National Health Commission, WS/T 428-2013) | 18.5–23.9 | 24–27.9 (超重) | 28 and over (肥胖) |
| Indonesia (Ministry of Health, Permenkes 41/2014) | 18.5–25.0 | above 25.0 to 27.0 (gemuk) | above 27.0 (obese) |
| Thailand (Department of Disease Control) | 18.5–22.9 | 23.0–24.9 (obesity level 1) | 25.0 and over (levels 2 and 3 from 25 and 30) |
Two details are easy to miss. Japan has no separate overweight class: 25.0 is already obesity of the first degree. Indonesia's ranges include their upper limit: a BMI of exactly 25.0 is still normal there, while it is overweight under the WHO classes and obese in Korea and Japan. Indonesia also splits underweight into "sangat kurus" below 17.0 and "kurus" from 17.0 to below 18.5.
Why the Same Number Means Different Things
BMI is a screening measure, not a diagnosis. It does not separate fat from muscle and does not show where fat is stored, which is why waist size is often measured as well. Standards with lower cut-offs aim to catch the higher health risk that appears at a lower BMI in their populations. Use the standard your doctor or health check uses; the BMI calculator lets you pick any of them on any language page, so a Korean living in Germany can still check the Korean classes, or a traveller the WHO ones.
Rounding at the Limits
The official tables write their limits with one decimal place. The calculator therefore reads the class from the BMI rounded to one decimal, the figure it shows. A BMI of 24.96 shows as 25.0 and falls in the class that starts at 25.0, so the class matches the number on the screen.
Healthy Weight for Your Height
The calculator shows the normal range for your height as the lightest and heaviest weights, to 0.1 kg, whose BMI rounded to one decimal is in the normal class. At 1.70 m that is 53.4 to 72.1 kg under the WHO classes (a BMI from 18.45 to just under 24.95) and 53.4 to 66.3 kg under the Korean and Thai classes.
Frequently Asked Questions
Is a BMI of 23 overweight?
Not under the WHO or US CDC classes, where normal runs to 24.9. It is pre-obesity in Korea, overweight or obesity level 1 in Thailand, and overweight under the NICE thresholds for South Asian, Chinese and some other groups.
Why does China use 24 and 28?
They are the limits of China's adult weight standard WS/T 428-2013, which the National Health Commission's 2024 weight management guidance applies: normal from 18.5 to below 24.0, overweight from 24.0 to below 28.0, obesity from 28.0.
Does BMI apply to athletes and older people?
With care. Muscle is heavier than fat, so athletes can have a high BMI without excess fat, and NICE advises interpreting BMI with caution in people aged 65 and over.
Sources
Source: CDC: Adult BMI Categories; WHO: Body mass index (BMI) · Last checked:
Source: NICE NG246, recommendation 1.9.11 · Last checked:
Source: e-나라지표: 비만 유병률 (질병관리청); 하남시 보건소: 신체질량지수(BMI) · Last checked:
Source: 厚生労働省 e-ヘルスネット: BMIチェック · Last checked:
Source: 国家卫生健康委：居民体重管理核心知识（2024年版）释义 · Last checked:
Source: Permenkes No. 41 Tahun 2014 tentang Pedoman Gizi Seimbang (Lampiran, hlm. 21-22) · Last checked:
Source: กรมควบคุมโรค กระทรวงสาธารณสุข: สถานีสุขภาพ (Health Station) · Last checked: