BMI Calculator
Enter height and weight to compare WHO and Korean adult BMI ranges at once.
- Fewer clicks, keyboard friendly
For adults. BMI categories for children and teens use age- and sex-specific growth charts.
BMI = 65 kg ÷ (1.7 m × 1.7 m) = 22.5
BMI is a screening measure, not a diagnosis. Pregnancy, high muscle mass, and body composition can make it less representative.
How to use
- Choose Metric or US customary units.
- Enter your height and weight.
- Read your BMI and the WHO and Korean adult categories.
- Compare the two healthy-weight ranges for your height.
How BMI is calculated
BMI is weight in kilograms divided by height in metres squared: kg/m². For example, 65 kg at 1.70 m is 65 ÷ (1.70 × 1.70) = 22.5. In US customary units, the equivalent shortcut is 703 × weight in pounds ÷ height in inches squared. This calculator converts US measurements before applying the same metric formula and rounds the displayed BMI to one decimal place.
Why the two adult ranges differ
The international adult categories used by the CDC place healthy weight at BMI 18.5 to below 25, overweight at 25 to below 30, and obesity at 30 or higher. The Korean Society for the Study of Obesity 2022 guideline uses 18.5 to below 23 as normal, 23 to below 25 as pre-obesity, then obesity classes starting at 25, 30, and 35. Showing both makes the different interpretation explicit instead of silently choosing one standard.
Use BMI as one screening signal
BMI estimates weight relative to height; it does not directly measure body fat or distinguish fat from muscle. CDC notes that a clinician considers BMI alongside medical history, health behaviours, examination, and laboratory findings. Adult BMI cutoffs are not used for children and teens, whose results are interpreted with age- and sex-specific percentiles. Pregnancy and unusually high muscle mass can also make a BMI result less representative of body composition.
Frequently asked questions
How do I calculate BMI?
BMI is calculated as weight in kilograms divided by height in metres squared. A person who weighs 65 kg and is 1.70 m tall has a BMI of 22.5 because 65 ÷ 1.70² equals about 22.5.
What is a healthy BMI range for adults?
The WHO-style international adult range is BMI 18.5 to below 25. The Korean Society for the Study of Obesity defines the normal adult range as BMI 18.5 to below 23, so the healthy-weight range calculated from the same height is narrower.
Why does the Korean BMI category differ from the WHO category?
The Korean Society for the Study of Obesity classifies BMI 23.0 to 24.9 as pre-obesity and BMI 25.0 or higher as obesity, while the international adult categories call BMI 23.0 to 24.9 healthy weight and start overweight at 25.0.
Can BMI diagnose obesity or health problems?
No. BMI is a screening measure rather than a diagnosis because it cannot measure body fat directly or distinguish fat from muscle. A health professional can interpret it with other health information when that is needed.
Is this BMI calculator suitable for children?
No. Adult BMI categories are not suitable for children and teenagers. CDC uses age- and sex-specific BMI-for-age percentiles for people aged 2 through 19 instead of the adult cutoffs shown here.
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Updated 2026-10-13