BMI formula

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BMI formula
For Australians

Height (m)

Weight (kg)

BMI 0  (0.00)


The BMI formula is for both adult men and women. Only height and weight are used by the BMI formula. The BMI formula does not factor in age or sex.

A question people often want to know, is what weight should they be according to the BMI scale. The BMI formula web app conveniently shows the weight for the BMI ranges for your height.



BMI formula

BMI stands for Body Mass Index. The BMI formula is calculated as the weight of a person in kilograms, divided by the square of their height in metres.

BMI formula


Enter weight in kilograms.


Enter height in metres.


BMI is often displayed as a whole number with no decimal. Often when dieting, it is good to see who close we are to the next BMI number. Since we measure our weight to 0.1 kg, I found including two decimals shows the change in the BMI number as the weight changes 0.1 kg. This figure has been included for convenience.

BMI - Body Mass Index (Adults)
Severely underweight: less than 16.5
Underweight: from 16.5 to 18.5
Normal: from 18.5 to 25
Overweight: from 25 to 30
Obese Class I: from 30 to 35
Obese Class II: from 35 to 40
Obese Class III: over 40 over
(Source: Wikipedia)

Interesting things about BMI 

  • The basis of BMI was developed by Adolphe Quetelet who was was a Belgian astronomer, mathematician, statistician and sociologist. In 1972 Ancel Keys coined the term BMI or body mass index.
  • From memory the healthy range in Australia was considered to be 20-25 and you may still see this range referenced on the internet. I noticed the healthy range changed to 18.5 to 25, but I'm not sure when this occurred.
  • BMI differs for some different races.
  • I often wonder about the BMI. The original formula was to describe a population and not individuals. Statistics often feature a bell curve with confidence intervals. As you are taller or shorter than the average how reasonable is the BMI figure. I've read suggestions the squaring of the height (the exponent of 2) perhaps should be 2.3 or 2.7. I found this work by a mathametician L N Trefethen who used 2.5 as the exponent was interesting. My concern however is the formula should reflect the real world and not just adjusted mathematically. Given we have so much more readily available data, perhaps the data should be reviewed and the formula be adjusted.
  • In the 1800s the average height in Europe was 167 cm and is now 178. The concept of BMI was developed in the 1800s.

Dieting related calculators

If you like BMI formula, you may wish to try one of the many other calculators or web apps I've created. Thank you for visiting the BMI formula site.

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The BMI formula web app comes with no warranty expressed or implied. The BMI formula web app is only for informational purposes and is not guaranteed to be error free. The information on this page is not intended to be advice.


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