How to use
Enter your height (cm) and weight (kg) to see your BMI and weight category under the Korean (KSSO) standard. The bar under the result shows where you fall and the weight at each threshold for your height.
Korean standard: KSSO (adults 19 and older)
The Korean Society for the Study of Obesity (KSSO) guideline 2024 (9th edition) classifies a BMI under 18.5 as underweight, 18.5–22.9 as normal, 23–24.9 as pre-obesity, 25–29.9 as class I obesity, 30–34.9 as class II obesity, and 35 or more as class III (severe) obesity. The thresholds are the same as in the previous (2022) edition. The current guideline treats obesity as a chronic disease that needs treatment, and its Korean category names use the word for “obesity disease.” This calculator classifies your result using the BMI rounded to one decimal place, so the number you see always matches the category.
How Korea’s obesity standard has changed
KSSO’s BMI thresholds (18.5, 23, 25, 30, 35) and its abdominal obesity threshold (waist circumference of 90 cm for men and 85 cm for women) have not changed since 2018. What has changed is the names of the categories and whether BMI alone is used for the assessment.
- 2018 — Obesity at a BMI of 25 or more was split into three classes, adding class III (severe obesity) at 35 or more. Before that, everything at 30 or more was grouped as class II.
- 2020 — The ranges and waist thresholds stayed the same.
- 2022 — Same ranges; the categories were called pre-obesity (23–24.9) and class I–III obesity (25 and above).
- 2024 (current) — The ranges stayed the same, but the Korean names changed to “pre-obesity disease” and “class I–III obesity disease.” The same year, the research institute of Korea’s National Health Insurance Service proposed raising the obesity threshold to a BMI of 27, but KSSO said it should stay at 25, where comorbidities start to rise.
- 2026 draft (not final) — Assessment will no longer rely on BMI alone but will also use waist measures. With a BMI of 25 or more, exceeding either the waist circumference threshold or a waist-to-height ratio of 0.5 counts as obesity (excess body fat); below 25, both must be exceeded. If obesity comes with a related condition such as type 2 diabetes or high blood pressure, or limits daily activities, it is classified as “obesity disease.”
This calculator uses the current 2024 standard and will be updated once the final 2026 guideline is published.
Body image in numbers: Korean adults
KSSO analyzed data on adults aged 20 and older from the 9th Korea National Health and Nutrition Examination Survey (2022–2024). The higher the BMI, the more likely people were to see themselves as obese, but the gap between categories was large: 77.5% of people with class I obesity and more than 90% of those with class II or higher saw themselves as obese, compared with only 48.1% of those in the pre-obesity range. At the same BMI, people aged 65 and older were less likely to see themselves as obese, and women tended to see themselves as obese at a lower BMI than men. That is why it helps to check the numbers rather than rely on how you feel.
Lifestyle tips from KSSO
We grouped KSSO’s “10 rules for overcoming and preventing obesity” into five themes and added the figures recommended in the 2024 guideline.
- Set realistic goals — Instead of trying to lose a lot at once, aim first for 5–10% of your current weight. The guideline notes that this much weight loss alone can reduce obesity-related symptoms and complications. The goal is better health rather than a number, and it is fine to pick up again if a plan slips once or twice.
- Change how you eat — Eat regular meals without skipping and include a variety of nutrients. Taking about 20 minutes per meal and chewing slowly can help you avoid overeating. Keeping high-calorie snacks out of sight and drinking water or tea instead of sugary drinks also reduces cues that trigger your appetite.
- Move more often — For weight loss, the guideline recommends at least 150 minutes of aerobic exercise such as walking or cycling per week (3–5 days a week), combined with strength training 2–3 days a week. Outside workouts, add everyday movement such as taking the stairs. If you have heart or kidney disease or have been inactive, talk to a doctor before starting.
- Manage sleep and stress — Get enough regular sleep, and make time to look after yourself so that you do not turn to food to cope with stress.
- Get professional help when needed — If it is hard to manage on your own, seek medical help. The guideline recommends considering medication for adults with a BMI of 25 or more who have not been able to lose weight with diet and exercise alone.
Limits of BMI
BMI was designed as a quick way to gauge weight status across large populations. People with the same BMI can differ in health depending on muscle mass, fat distribution, age, and sex. Abdominal obesity in particular does not show up in BMI, so it is worth checking your waist circumference as well. Waist thresholds also differ by country, and the Notes section of the result shows the threshold for this standard. Results are for reference only and are not a medical diagnosis.