How to calculate BMI / Calculating BMI

The BMI is calculated using a simple formula.

Calculating BMI

BMI is a measure of height in relation to weight, resulting in an index number indicating the ratio of weight to squared height (kg/m2).

Traditional BMI

BMI is calculated by dividing weight (kg) by the square of height (kg/m2). BMI is the most popular and practical weight-based indicator for measuring overweight and underweight.

An easy way to calculate a traditional BMI is to divide the weight twice by the height. For example, 77 kg / 1.77 m / 1.77 m is about 24.6.

A new way to calculate BMI

Opinions vary when it comes to the truthfulness of the traditional BMI. Mathematician Nick Trefethen from the University of Oxford has developed a new formula for calculating BMI that, according to him, takes into consideration e.g. the distortion resulting from height.

In Trefethen's formula, the weight coefficient is the square root of the average human height, 1.69m. He explains the power of 2.5 in that people are not two-dimensional so weight should not be measured on this basis either.

Traditional mathematical formula

`"BMI" = "Weight[kg]" / ("Length[m]"^2)`

New mathematical formula

`"New BMI" = "1,3 Weight[kg]" / ("Length[m]"^"2,5")`

Sources and more information
  1. Nick Trefethen: BMI
  2. BMI: Does the Body Mass Index need fixing

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