BMI (Body Mass Index) is your weight in kilograms divided by the square of your height in meters. It is the most widely used screening measure for judging whether your weight is appropriate for your height. Because it needs nothing but your height and weight, it serves as a baseline reference in health checkups, diet planning, insurance underwriting, and many other settings. This calculator works out your BMI the moment you type your numbers and shows, with a color gauge, where you fall across six categories from underweight to severe obesity, using the Asia-Pacific cutoffs of the Korean Society for the Study of Obesity (KSSO).
Research shows that, at the same BMI, people of Asian descent tend to carry more visceral fat and face a higher risk of metabolic disease than people of European descent. For that reason the KSSO applies lower cutoffs than the general World Health Organization (WHO) thresholds: a BMI of 23 or higher is classified as overweight, and 25 or higher as obese. This tool reflects those Korean cutoffs, so it is well suited for comparing against domestic health-checkup results. Every calculation runs entirely inside your browser; the height and weight you enter are never sent to a server or stored.
How to Use
- 1
Enter your height
Enter your height in centimeters (cm). For example, for 170 cm, just type 170.
- 2
Enter your weight
Enter your current weight in kilograms (kg). Decimal values are supported.
- 3
See the result
As you type, your BMI, weight category, and the healthy weight range for your height are shown automatically.
- 4
Copy the result
Press the copy button to copy the result as text and paste it into a note or messenger.
When It's Useful
Compare with a health checkup
Quickly see which category the BMI on your checkup report falls into and what your healthy weight range is.
Set a diet goal
Compare your current BMI with the upper end of the healthy range to estimate how many kilograms to lose to get back into range.
Prepare for insurance or a physical
When insurance underwriting or a physical exam asks for a BMI threshold, check your value in advance.
Check the family's health
Run your parents' or children's height and weight to review their weight category together and start a conversation about health.
Tips
- BMI cannot tell muscle from fat. An athlete with high muscle mass may show a high BMI without being obese, so pair this with a body-fat calculator.
- Standard adult BMI cutoffs do not apply directly to growing children and teens, pregnant women, or the elderly, so treat the result as a rough reference only.
- If you want to track weight changes, measure at the same time each day (for example, in the morning on an empty stomach) for consistency.
- Even with a BMI in the healthy range, abdominal obesity (a large waist) can mean a higher metabolic risk, so it helps to check your waist circumference too.
- This calculator uses the KSSO cutoffs (overweight at 23, obese at 25). Results may differ from overseas sources or WHO cutoffs (overweight at 25, obese at 30).
- BMI is just a snapshot at one point in time. Rather than dropping weight rapidly, staying steadily within the healthy range is better for your health.
FAQ
How is BMI calculated?
BMI = weight (kg) / (height (m) x height (m)). For example, at 170 cm and 65 kg: 65 / (1.7 x 1.7) is about 22.5.
Are the Korean cutoffs different from the WHO cutoffs?
Yes. The general WHO thresholds treat a BMI of 25 or higher as overweight and 30 or higher as obese, but the KSSO reflects Asian characteristics and classifies more strictly: 23 or higher as overweight and 25 or higher as obese. This calculator uses the Korean cutoffs.
How are the BMI categories divided?
This calculator uses six categories: underweight (below 18.5), normal (18.5–22.9), overweight (23–24.9), obesity I (25–29.9), obesity II (30–34.9), and severe obesity (35 and above).
My BMI is normal but I have a belly. Is that okay?
Even with a normal BMI, you can have a lot of visceral fat — so-called normal-weight obesity. It is a good idea to also check your waist circumference (abdominal obesity is 90 cm or more for men, 85 cm or more for women) and your body-fat percentage.
What is the basis for the healthy weight range in the result?
It is the weight range corresponding to a BMI of 18.5–22.9, applied to your height. Within this range, your weight is considered healthy relative to your height.
Can I enter decimal values for height or weight?
Yes. You can enter decimals such as 165.5 cm and 58.3 kg for a more precise BMI.
Is the height and weight I enter stored?
No. All calculations run only in your browser and your input is never sent to a server. When you close the page, all data is gone.
Can BMI alone diagnose obesity?
BMI is a screening measure, not a diagnostic tool. An accurate assessment of obesity and overall health must be made by a medical professional and may include body-composition analysis, blood tests, and more.