BMI Calculator
Enter your height and weight to calculate your Body Mass Index (BMI), obesity classification per Korean Society for the Study of Obesity criteria, and standard body weight.
Frequently Asked Questions
How is BMI calculated?
BMI (Body Mass Index) = weight (kg) ÷ height (m)². For example, a person who is 170 cm (1.7 m) tall and weighs 65 kg has a BMI of 65 ÷ 1.7² ≈ 22.5.
What are the obesity classification thresholds?
This calculator uses the Korean Society for the Study of Obesity (2018 Clinical Practice Guidelines) criteria: Underweight < 18.5, Normal 18.5–22.9, Pre-obese (overweight) 23–24.9, Obesity Class I 25–29.9, Obesity Class II 30–34.9, Obesity Class III (severe obesity) ≥ 35. These ranges differ from the WHO international standard (overweight ≥ 25, obese ≥ 30), so results may differ when compared with international references.
How is standard body weight calculated?
Standard body weight is the weight (kg) at which BMI equals exactly 22: weight = 22 × height (m)². BMI 22 is widely used as the standard because it is statistically associated with the lowest disease risk.
Does a high BMI always mean poor health?
Not necessarily. Because BMI cannot distinguish between muscle and fat, people with high muscle mass may have a high BMI without excess body fat. Conversely, "thin-fat" individuals — low muscle, high body fat percentage — can have a normal BMI yet still face health risks. Use BMI as a reference indicator only.