Step 1: Confirm it's percentage decrease

The first thing I’d recommend doing is putting a little minus sign on your working sheet to remind you that you’re doing percentage decrease rather than increase.

Step 2: Calculate the difference

Next, you need to work out what the change is so take the new number of 1,975 and minus the original number 2,480. This gives the answer of -505.

Step 3: Divide the difference by the original

Next you need to work out what this answer is in comparison to the original number so that’s 505 in comparison to 2,480. To do this, divide -505 by 2,480 and you get the answer of -0.2036.

Step 4: Convert to percentage

All we need to do now is turn this into a percentage by multiplying by 100. This gives us 20.4%. If your keep doing this over and over, you can start to shorten the steps down so all you need to do is take the new number minus the original number, divide this by the original number and multiply by 100.