Although the BMI can be calculated by dividing the weight in kilograms over the square of height in meters directly, this is often difficult using a simple calculator at the bed side because in this case we have to determine the square of the height in meters (which might contain a coma) and then we should save it in our minds or on the calculator (both tasks are difficult!) then to use it as the denominator for the formula. While the formula seen above it has two advantage 1 the height is in centimeters so no coma confusion 2 straight forward mathematics and no need to save values

