How to calculate percentages:
First, work out the difference between (increase) the two numbers you're comparing.
Increase = New number - Original number
Then, divide the increase by the original number and multiply the answer by 100.
% increase = Increase divided by the Original number times 100.
If your answer is a negative number than it is a percentage decrease. (You'd pretty much have to do the same thing that you do for the percentage increase except you'd get a positive number.)
