HOW TO CALCULATE PERCENTAGE CHANGE
PART AND WHOLE
A percentage is a way of showing a part out of a whole. The figure 85% means 85 out of 100. Therefore, in order to find percentage change, you'll need two pieces of information: the part (amount of change) and the whole (the original amount).
Let's follow the example of a chess club that began with 8 members and ended up with 14 members. What is the percent change in membership?
STEP 1: FIND THE AMOUNT OF CHANGE
Calculate the difference, or the change in values. You can do this by subtracting the smaller number from the larger number.
In this example, you'll end up with 6.
STEP 2: DIVIDE
Since a percentage is a part out of a whole, divide the part (the change you just calculated) by the whole. Always use the original value as the whole – that's because you're calculating how much this original value changed. In this case, the whole is the original 8 members.
Our figure here is 0.75.
STEP 3: MULTIPLY
In order to change this figure to a percentage, simply multiply by 100.
This gives us a solution of 75. Just add a % sign to the end and you are done! The chess club membership changed by 75% and was, more specifically, a 75% increase.
What would the calculation look like if the chess club had lost members? Suppose they began with 8 members and ended up with 6 members.
Step 1: 8 – 6 = 2
Step 2: 2 ÷ 8 = 0.25
Step 3: 0.25 x 100 = 25
There was a 25% decrease in membership! Note that values can increase more than 100%. If the price of a movie ticket increases from $5 to $12, that is a 140% increase (it more than doubled). Values do not normally decrease more than 100% because that would bring the value below zero.