Knowing how to calculate percent change means we can put pay increases, spending increases and other amount changes into perspective. Here's the formula, expressed as an algebra equation:
(new amount - old amount)/old amount = change
Here it is expressed in English: Take the amount of change (new minus old), divide it by the old amount and you'll get the percent change.
This formula works whether you're dealing with increases or decreases, which is handy in times of budget cuts, when decreases seem to be the norm.
So let's use an example that's obvious: If I was making $10 an hour last year and I'm making $12 an hour this year, what is my raise, or percent change?
(12-10)/10=0.2
The answer is 0.2, or 20 percent.
Now, just to be safe, you should double-check your math: Does 20 percent of $10 equal $2? Yes, it does. And yes, you really need to check, because I've seen reporters have to write ugly corrections because they got the formula backwards.
If you need to calculate percent change for a lot of figures, a spreadsheet can help with that. You write the formula just like the equation shown at the top of this post, substituting spreadsheet cell numbers. For the spreadsheet below, the formula is =(C3-B3)/B3.
Or, if you're feeling really lazy at the moment and you just want a quick answer, use the calculator below: Click on the "Click to edit" button, then drop your new and old figures in the appropriate white boxes below - just numbers, no commas or dollar signs. When you hit "enter" after typing in the second amount, the answer will appear automatically.
© Holly A. Heyser
