How to use
Enter your Height in cm and your Weight in kg. Result then gives your BMI and the category it falls in under the Korean Society for the Study of Obesity (KSSO) guideline, with the official Korean name of that category beside it. The calculator accepts heights from 50 to 250 cm and weights from 2 to 400 kg. BMI is your weight in kilograms divided by the square of your height in meters. At 165 cm and 60 kg, that is 60 ÷ (1.65 × 1.65) = 22.04, so you see BMI 22.0, Normal.
- Category bar: the six KSSO categories side by side, all the same width, with a vertical line at your BMI. Above the bar are the BMI cutoffs (18.5, 23, 25, 30, 35). Below it, each cutoff is turned into a weight in kg for the height you entered. On a narrow screen the category names and ranges move into a list under the bar.
- Notes: the waist circumference that counts as abdominal obesity, and what the guideline recommends when you have it.
- Copy: the copy button next to the BMI number copies a single line such as
BMI 22.0 (Normal).
BMI categories in the KSSO 2024 guideline
The KSSO obesity guideline 2024 (9th edition) sorts the BMI of adults into six categories. In its 2024 Obesity Fact Sheet, published the same year, KSSO called a BMI of 25 or more 비만병 (“obesity disease”) and 23–24.9 비만병전단계 (“pre-obesity disease”), and those are the Korean names this calculator shows. The cutoffs are the same as in the previous (2022) edition.
| Category (name on screen) | BMI | Weight where the category starts at 165 cm |
|---|---|---|
| Underweight | under 18.5 | |
| Normal | 18.5–22.9 | 50.4 kg |
| Pre-obesity | 23–24.9 | 62.6 kg |
| Class I obesity | 25–29.9 | 68.1 kg |
| Class II obesity | 30–34.9 | 81.7 kg |
| Class III obesity (severe) | 35 and above | 95.3 kg |
The last column is what you see under the bar when you enter a height of 165. One catch: this calculator rounds your BMI to one decimal place and then picks the category from the rounded number, so you can land in the higher category while weighing slightly less than the table says. At 165 cm, 62.5 kg works out to 22.96, which rounds to 23.0 and is shown as Pre-obesity, while 62.4 kg gives 22.9, Normal. This way the BMI on screen and the category name next to it never disagree.
How Korea’s obesity standard has changed
KSSO’s BMI cutoffs (18.5, 23, 25, 30, 35) and its abdominal obesity threshold (a waist circumference of 90 cm or more for men and 85 cm or more for women) have not changed once since 2018. What has changed is what the categories are called and whether BMI alone decides the result.
- 2018: Obesity at a BMI of 25 or more was split into three classes, with a new class III (severe obesity) at 35 or more.
- 2020: The ranges and waist thresholds were left as they were.
- 2022: Same ranges. The categories were called pre-obesity (23–24.9) and class I–III obesity (25 and above).
- 2024 (current): The 9th edition of the guideline left the ranges where they were, and KSSO’s 2024 Obesity Fact Sheet called them “pre-obesity disease” and “class I–III obesity disease” in Korean. That same year the research institute of Korea’s National Health Insurance Service proposed raising the obesity cutoff to a BMI of 27, and KSSO responded that it should stay at 25, the point where related conditions start to become more common.
- 2026 draft (not final): BMI no longer decides the result alone, and waist measures are checked too. With a BMI of 25 or more, meeting either the waist circumference threshold or a waist-to-height ratio (waist ÷ height) of 0.5 or more is enough to count as “obesity”, meaning excess body fat. Below 25, you have to meet both. If a related condition such as type 2 diabetes or high blood pressure, or a limit on daily activities, comes on top of that, it is “obesity disease”.
This calculator classifies by the BMI ranges of the current 2024 guideline only. It will be updated once the final 2026 guideline is published.
Why waist size matters too
Two people with the same BMI do not carry the same risk if one of them stores more fat around the belly, and height and weight alone cannot show that. So KSSO counts a waist circumference of 90 cm or more for men and 85 cm or more for women as abdominal obesity, and recommends that when abdominal obesity is present, the risk of related conditions be managed one level higher than the BMI category suggests. The two lines under Notes in the result say exactly this. The calculator does not take a waist measurement, so run a tape measure around your waist and compare the number with these thresholds yourself.
Body image in numbers: Korean adults
KSSO analyzed adults aged 20 and older in the 9th Korea National Health and Nutrition Examination Survey (2022–2024). The higher the BMI, the more people saw themselves as obese, but the gap between categories was wide. Among people in class I obesity, 77.5% saw themselves as obese, and in class II and above 90% or more did, yet in the pre-obesity range only 48.1% did. At the same BMI, people aged 65 and older were less likely to recognize their own obesity, and women tended to see themselves as obese at a lower BMI than men. That is a good reason to check the number once instead of going by how you feel.