Percentage increase tells us how much a number changed. Real world example: last week a bag of oranges cost five dollars and now it's six. What's the percentage increase? Let's start with just the increase. It was 5 and is now 6. It's 1 dollar more. How many percents does that equal? Let's see. The formula for percentage is:
percentage = 100 * numerator / denominator, where numerator is our increase (1) and denominator is our original value (5). So the formula for percentage increase is:
percentage increase = 100 * increase / original value
So in our example percentage increase = 100 * 1 / 5 = 100 / 5 = 20. The price of bag of oranges increased by 20%. Outrageous!
Let's practice a bit more. Last year my parents gave me $20 every week for my expenses. This year I negotiated it to be 25 dollars. I have my needs, you know... and don't even get me started on the inflation rate these days... . So what's the raise percentage-wise?
Percentage increase = 100 * 5 / 20 = 500 / 20 = 25 percent. Not bad, given I spent like 5 minutes negotiating and was juggling chickens at the same time.
Try entering some numbers into the form below:
Calculating percentage decrease is very similar (they are the two sides of the same coint - a percentage change). When comparing two percentages, it's often easier to just use percentage points. Also, you may want to read how to calculate percentage in case you have not already.