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BMI Calculator

What is BMI?

BMI (Body Mass Index) is an indicator that shows the relationship between weight and height, and is widely used to evaluate obesity. BMI is an internationally recognized index and is also used as a guide for health management and dieting, as it can be easily calculated.

How to Calculate BMI

BMI is calculated by dividing weight (kg) by height (m) squared. It can be expressed by the following formula:

BMI = weight (kg) / height (m)²

For example, if you are 170cm tall (1.7m) and weigh 65kg, your BMI can be calculated as follows:

BMI = 65 / (1.7 × 1.7) ≈ 22.5

Classification of BMI by the World Health Organization (WHO)

According to the World Health Organization (WHO), BMI is classified as follows, and health risks vary depending on the range:

  • Underweight: BMI < 18.5
  • Normal weight: 18.5 ≤ BMI < 25
  • Overweight: 25 ≤ BMI < 30
  • Obese (class 1): 30 ≤ BMI < 35
  • Obese (class 2): 35 ≤ BMI < 40
  • Obese (class 3): BMI ≥ 40

Advantages and Limitations of BMI

The advantage of BMI is that it can be easily calculated from height and weight and is widelyused as an indicator of obesity. However, there are also limitations to BMI, such as the following:

  1. Does not take into account muscle mass or body fat percentage: BMI alone may not accurately determine obesity in individuals with varying amounts of muscle mass or body fat percentage, such as muscular individuals or the elderly.
  2. Individual differences: Due to factors such as age, gender, and genetics, there can be significant individual differences in health status even with the same BMI value.
  3. Does not directly assess disease risk: BMI is an indicator of obesity, but it does not directly evaluate disease risk. Other indicators or test values should be considered for risk assessment.


BMI is an easy-to-calculate indicator of obesity and is useful for health management and dieting. However, it is important to evaluate health status using other indicators in conjunction with BMI, taking into account factors such as muscle mass and body fat percentage, individual differences, and disease risk assessment.