BMI Calculator

What is BMI?

Body mass index (BMI), or Quetelet Index, is an attempt to estimate the mass of tissue (muscle, fat and bone) in an individual to identify their fitness level. Although proposed in 1830 by Adolphe Quetelet as the eponymous Quetelet Index, it wasn't until 1972 that the now popular term BMI came into existence. It is measured simply as a ratio of weight (in Kgs) to the square of height (in metres). See our detailed table for information on the fitness categories based on BMI.

Factoid

To discourage anorexia, many countries, including France, Israel, Italy and Spain have banned models below a BMI of 18.5 from the fashion shows.

What do the BMI scores mean?

Fitness categories based on Body Mass Index (BMI), as published by World Health Organization (WHO)
Fitness Category BMI BMI Prime
Very severely underweight less than 15 less than 0.60
Severely underweight from 15 to 16 0.60 to 0.64
Underweight from 16 to 18.5 from 0.64 to 0.74
Normal or Healthy from 18.5 to 25 0.74 to 1.0
Overweight 25 to 30 1.0 to 1.2
Moderately obese 30-35 1.2 to 1.4
Severely obese 35 to 40 1.4 to 1.6
Very severely obese Over 40 over 1.6

The ABSI scores should be compared with the average scores of the people of same age and gender. Significantly higher scores indicate higher health risks.

Individuals categorized as overweight or obese according to BMI scores as typically considered to be at a higher risk for many life threatening diseases such as coronary heart disease, Dyslipidemia, Type 2 Diabetes, Gallbladder disease, Hypertension, Osteoarthritis, Sleep Apnea, and several forms of cancer, including endometrial, breast, and colon cancer.

Factoid

Interestingly, recent research has shown that overweight individuals, or those having a BMI score between 25 and 29.9, have a lower overall mortality than all other categories.

This obesity-mortality paradox is now driving research into novel alternative metrics as well as to improve our understanding of what it really means to be obese.

Limitations of BMI

Among its many limitations, BMI does not scale well with height. For example, taller individuals typically end up having a higher BMI score than their shorter counterparts with similar health profile.

Similarly, BMI also ignores variation in physical characteristics, such as large or small frame size. For example, the body fat percentage of a smaller framed person might be high but still not result in a high BMI score. On the contrary, a large framed person, with lean body composition might still have a higher BMI.

Also, the BMI score is independent of gender. It is well-known that men and women store body fat differently, and that men typically need lower fat reserves than women. So for the same height and weight combination, and thereby same BMI, two individuals can be drastically different in their health profiles, just because they belong to different genders. It is interesting to note though that the World Health Organization (WHO) has not created gender-specific BMI fitness categories.

Thus, several in the research community have questioned the suitability of BMI as a fitness estimate. Owning to these reasons, BMI can actually be quite inaccurate and misleading.

Better alternatives?

Body fat percentage is widely regarded as a better estimate of fitness, as gender-specific guidelines are known.

Body mass index

The body mass index (BMI) or Quetelet index is a value derived from the mass (weight) and height of an individual. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m2, resulting from mass in kilograms and height in metres. The BMI may also be determined using a table or chart which displays BMI as a function of mass and height using contour lines or colors for different BMI categories, and may use two different units of measurement. The BMI is an attempt to quantify the amount of tissue mass (muscle, fat, and bone) in an individual, and then categorize that person as underweight, normal weight, overweight, or obese based on that value. However, there is some debate about where on the BMI scale the dividing lines between categories should be placed. Commonly accepted BMI ranges are underweight: under 18.5 kg/m2, normal weight: 18.5 to 25, overweight: 25 to 30, obese: over 30. . Read more...