How to use the percent button on a calculator

If you have a percent button in your calculator you might be wondering how to use it or what is it used for?!
Percent in calculators used to quickly figure things like the price of items on sale, calculate tax ... etc

So how percent on Calculators function?

This is tricky, because unlike other operators like (+ , - , ×, ÷), percent doesn't always behave the same, it depends on the pervious operator.  let me show you different scenarios

Case 1: Percent after '+' operator

This add percent to the original number, for example suppose you want to compute how much a $80 t-shirt will cost after including 5% tax 
The answer is $84 which is correct since 5 percent of 85 = 4 adding it to 85 results 84

Case 2: Percent after '-' operator

Suppose the same t-shirt is on sale and it's price is off by 20%, in this case we use the - operator
80 - 20 %
Captured using Calculator+ by xNeat
The answer is $64, because 20 percent of 80 is 16, subtracting it from 80 the result is 64

Case 3: Percent with '-' and '+' operators

Now we have a t-shirt that cost $80, and is on sale 20% off, with 5% sales tax
We calculate 80 - 20% + 5%
80 - 20% + 5%
Captured using Calculator+ by xNeat
The answer is $67.2 since 20% of 80 = 64, then we add 5% to get 67.2, in this case the order doesn't matter, '80 + 5% - 20%' will give us the same result

Case 4: Percent with '×' operators

Suppose we want to know how much we save by buying a $80 t-shirt that is on sale 20% off.

We calculate 80 × 20%
80 - 20% + 5%
Captured using Calculator+ by xNeat

The result is 16, which is correct since 80 × 0.2 = 16

Case 5: Percent with '÷' operators

This one is barely used,  80 ÷ 20% is equivalent to '80 x (1/0.2)'
So to sum things up, use % with '-' for sales, % with '+' for taxes!
You are ready now to take the percent button on your calculator to the next level!


If you want a percent calculator for your iPhone that preserve the order of operation, you can give Calculator+ by xNeat a try, it's FREE, download it from the App Store.