How to Use a Calculator for Percentages

Learn to use the percent key on your calculator.

Have you ever wondered how to use the percent key on your calculator? Yes, it is meant to help you calculate percentages. Learn to use it, and your life will become a lot easier.

Here are a few tips and examples that show how to use a calculator to quickly figure percentages.

Instructions

1. Note that not all calculators behave the same way as far as the percentage key is concerned. Thus, test the examples in this article on your calculator. If your calculator does not have the percent key or does not behave in the way described here, don't despair - you can still use it to calculate percentages, it's just that you will have to press a few more buttons.

2. Let's calculate a tip on your restaurant bill. Suppose your bill happens to be $64.35 and you would like to leave 15% tip.

   Type the following into your calculator: 64.35 * 15 %
   Answer: 9.6525 or $9.65 after rounding.

   Most simple calculators will give an answer right here without having to press the = sign. If yours does not, press = and see if you get the right answer.

   Alternatively, you can calculate this percentage by typing in
   64.35 * 15 / 100 or 64.35 * 0.15

   Thus, you may have observed that all that the percent key did here was division by a hundred.

3. Let's calculate a grade percentage - say you got 34 out of a maximum of 40 points.

   To figure out your grade percentage type in: 34 / 40 %
   Answer: 85

   Alternatively, without the percent key: 34 / 40 * 100

4. Let's calculate a sale price on those shoes that originally cost $139, but are now discounted by 35%.

   On your calculator type in: 139 - 35 % =
   Answer: 90.35 or $90.35

   This calculation is amazingly easy with the percent key! Alternatively, you would first have to calculate what the 35% of the $139 is and then subtract it from 139:
   139 * 35 / 100 = 48.65
   139 - 48.65 = 90.35

5. Let's calculate multiple discounts on an item and add the sales tax. Suppose those shoes from previous step went on clearance for an additional 40% off. So we have 35% off and then 40% off on top of that, and then we want to add 5% sales tax.

   Again, it's easy with the percent key: 139 - 35 % - 40 % + 5 % =
   Answer: 56.9205 or $56.92 after rounding.

   So you can add or subtract any increases or decreases in percentages using the percent key.

   It gets a bit more involved to do this without the percent key, however. You would have to do it the same way as in step 4 for each subsequent percentage increase or decrease. Please see an article on calculating sale prices for more detailed explanation on this.

6. In summary, the percent sign works with all 4 basic operators: multiplication, division, addition, and subtraction.

   - Use multiplication to calculate a percentage of a number, such as figuring out a tip.
   - Use division to figure out what percentage one number is of another, such as calculating a grade percentage from a maximum.
   - Use addition and subtraction for calculating percentage increases or decreases such as figuring out markups or discounts.

Tips & Warnings

• Test the percent key on your calculator to make sure it behaves like you expect it to.

Resources

• How to Figure Out Sale Prices
• How to Find Percentage Change in Price
• How to Learn Percentages