BMI Calculator
Body mass index from height and weight, with a category and healthy weight range, using the Korean 18.5 / 23 / 25 cutoffs.
How to use
- Enter your height in centimetres (for example 170).
- Enter your weight in kilograms (for example 65). Decimals are fine.
- The BMI value, the category (underweight, normal, overweight, obese) and the healthy weight range for your height appear at once.
- Copy result copies the answer, and Share with inputs copies a link with your height and weight filled in.
FAQ
How is BMI calculated?
Weight in kilograms divided by height in metres squared. At 170 cm and 65 kg that is 65 ÷ 1.7² ≈ 22.5, which is in the normal range.
Which cutoffs does this calculator use?
The adult cutoffs of the Korean Society for the Study of Obesity (2020 and 2022 guidelines): under 18.5 underweight, 18.5–22.9 normal, 23–24.9 overweight (pre-obese) and 25 or above obese. The category is decided from the value shown to one decimal place, so 25.0 counts as obese.
Why do these differ from the WHO cutoffs?
The global WHO cutoffs are 25 for overweight and 30 for obesity. Korean guidelines follow the Asia-Pacific cutoffs of 23 and 25 because health risks rise at a lower BMI in Asian populations. A BMI of 24 is ‘overweight’ here but ‘normal’ by the WHO table, and 27 is ‘obese’ here but ‘overweight’ by the WHO table.
Are all values of 25 and above the same?
This calculator labels everything from 25 up as ‘obese’. The Korean guideline splits it into class 1 (25–29.9), class 2 (30–34.9) and class 3 (35 or above). A height of 175 cm and a weight of 80 kg gives a BMI of 26.1, which is class 1.
How is the healthy weight range worked out?
Height in metres squared, multiplied by 18.5 and by 22.9. For 170 cm that is 53.5–66.2 kg; for 160 cm it is 47.4–58.6 kg.
Does it accept pounds and inches?
No, only centimetres and kilograms. Convert first (1 in = 2.54 cm, 1 lb = 0.4536 kg): 5 ft 7 in and 143 lb is about 170 cm and 65 kg.
Does BMI alone judge health?
No. BMI cannot tell muscle from fat, so a muscular person can score high. The Korean guideline also looks at waist size (90 cm or more for men, 85 cm or more for women signals abdominal obesity). It is also an adult measure, not for children or pregnancy.