How to Add and Subtract Percentages on a Calculator

Smartphone calculator app displaying numeric keypad

If your phone calculator does not have a percentage button, figuring out store sales or sales tax can feel tricky. I’ll show you an easy multiplication shortcut that works on any basic calculator.

1. Enter Your Starting Number

Type the base price or total amount on your calculator keypad (for example, **300**).

Typing the starting number 300 on the calculator keypad
Enter Starting Amount on Keypad

2. Tap the Multiplication Sign

Tap the **x** (multiplication) button.

Entering multiply 1.2 to calculate 300 plus 20 percent equaling 360
Multiply by 1.2 to Add 20 Percent

3. Add Percentages Using 1.X

To add a percentage, multiply by **1** plus your percentage as a decimal. For example, to add 20%, multiply by **1.20** and tap **=** to get **360**.

Entering multiply 0.8 to discount 300 minus 20 percent equaling 240
Multiply by 0.8 to Subtract 20 Percent

4. Subtract Percentages Using 0.X

To subtract a discount, multiply by **1** minus the percentage. For example, to take 20% off, multiply by **0.80** and tap **=** to get **240**.

Showing decimal adjustments for 10 percent tax and discounts
Use 1.1 or 0.9 for Ten Percent Calculations

5. Use the Same Trick for Other Rates

Multiply by **1.10** to add 10%, multiply by **0.90** to subtract 10%, or multiply by **1.05** to add 5% sales tax.

Helpful Tips

This decimal multiplier trick gives you the final total in a single calculation, eliminating the need to write down intermediate percentage amounts. For more everyday math and tech tips, check out our How-To guides hub.


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