Percentage difference between numbers

[luvfahad]

I understand that the formula to calculate an percentage increase between numbers is,


=(A1-B1)/B1


But when does one use =(A1-B1)/A1, is that the formula to show percentage decrease?

 

[Luke M]

No, it would be the same formula

=(A1-B1)/B1


Where A1 is new value, B1 is old value.

Example

Start with 100 units, end with 110 units. This is an increase of:

=(110-100)/100

=10/100

10%


If we start with 100 unites and end with 90, this is a decrease of:

=(90-100)/100

=(-10)/100

-10%


The sign of the number indicates whether it's an increase/decrease.

 

[Jordan]

Well, that all depends on which of the cells above are the original and new amounts. If we let A1 -> Original Amount and B1-> New Amount then the percentage increase and decrease formulas are as follows:


Percent Increase:

(B1-A1)/A1


and Percent Decrease:

(A1-B1)/A1


Both formulas always have this generalized form:

(POSITIVE DIFFERENCE) / (ORIGINAL AMOUNT)


Remember, the subtraction arithmetic in the numerator should always be positive - if it's not, then you are using the wrong measure. The denominator is always the original amount.

 

[Jordan]

This might be helpful for you, too:

http://www.buzzle.com/articles/calculate-percent-difference.html