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body mass index

Health Calculator: Body Mass Index

BMI is the abbreviation of Body Mass Index. Body mass index is a measure of body fat based on height and weight. It is applicable to men, women and children.

It is defined as the ratio between weight of an individual in kg and height of the same person in m2. The body mass index is an attempt to measure the amount of tissue mass like muscle, fat, and bone in an individual. It then classifies that person as underweight, normal weight, overweight, or obese based on that value. A check of individual’s BMI tells whether that person is in a healthy state or not. The formula to calculate Body Mass Index is:

BMI =weight (kg) / Height (m2)

But the question is how to calculate your own body mass index and how to categories it?


As mentioned above, to calculate BMI we need two components. One is the measure of our weight and other is the measure of our height. You can measure your height in meters by asking someone using a measuring tape or by simply going to the doctor. Similarly, you can measure your weight through weight scale in kilograms.


Always remember, while measuring height, stand straight with head facing front without shoes and socks. And while measuring weight, keep clothing minimum, look ahead with empty stomach (meal should be taken at least 3 hours before the measurement).

Body Mass Index Classification

As per WHO (World Health Organization), body mass index is classified as follows:

Classification  BMI Range
Very severely underweight ≤ 15
Severely underweight 15 – 16
Underweight 16 – 18.5
Normal (healthy weight) 18.5 – 25
Overweight 25 – 30
Obese Class I (Moderately obese) 30 – 35
Obese Class II (Severely obese) 35 – 40
Obese Class III (Very severely obese) ≥ 40



Body mass index is applicable to both males and females belonging to all the age groups. The above classification of WHO is for age group 18 years and above that. But for infants, children and adolescents, different BMI categories are given by CDC (Center of Disease Control and prevention). But it is calculated using the same formula as adult BMI. Children and teen’s BMI need to be age and sex-specific. It is so, because the amount of body fat changes with age and the amount of body fat differs between girls and boys.

For example

If weight of a person is 60 kg, and height of that person is 2.52 m2, then the body mass index of that person will be

60 / 2.52 = 23.80 kg/m2

This value falls in the normal category. That is, the person has healthy weight, and is not undernourished or obese. The BMI ranges are based on the relationship between body weight, height, disease and death. Any value of BMI below 18.5 is the sign of undernourishment. The various health risks of being underweight (low BMI) are

  • compromised immune function
  • respiratory disease
  • digestive diseases
  • cancer
  • Osteoporosis

The value above 25 is considered as a sign of over nutrition which is also bad for health. It is a step towards poor health. Overweight and obese individuals are at an increased risk for the following diseases:

  • coronary artery disease
  • type 2 diabetes
  • gallbladder disease
  • Hypertension
  • Osteoarthritis
  • Stroke
  • At least 10 types of cancers

Both under nutrition and over nutrition are a type of malnutrition. Presently, it is affecting the developing countries most. The condition of underweight and overweight is co-existing in India and we should try to maintain our weight to fall in normal category.

Therefore, an individual should always have a good knowledge of their own body mass index. BMI calculator is a reliable way to determine whether a person has too much body fat or a person is malnourished. It is a quick method, and highly recommended gauge of determining health status.

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