A percentage increase or decrease in a value is calculated with respect to the intial value not the final value. If the proftis of this website were £28 in 2004 and £35 pounds in 2006 we calculate the increase like this:

( ( [2005 Value] - [2004 Value] ) / [2004 Value] ) * 100 = [% Increase or Decrease]
or
( ( 35 - 28 ) / 28 ) * 100 = 25%

The Calculator

Note: don't include anything other than numbers and a decimal point. For instance don't enter one thousand pounds like this "£1,000.00" enter it like this "1000.00".

First Value (eg the 2004 price):

Second Value (eg the 2005 price):

Note One: The result may include a large number of decimal places. This isn't an error. If you want fewer decimal places simply round where you need.

Note Two: Certain calculations may give results that are a tiny fraction out. This is because the calculation is done with floating point numbers (doubles to be precise) which can't accuratly represent all numbers. This is a common problem for computers. There are ways around this problem and they are used for doing calculations with money and other figures that can't lose accuracy. The error should be much less than one part per billion.