Introduction
The Add Percentage Calculator helps you add or subtract a percent from any number. Type in your number, pick + or −, and enter the percent. You get the answer right away, plus the steps that show how it was found.
This tool has two modes:
- Base + %: add or take away a percent of a number. For example, 200 + 15% = 230.
- % + %: add two percents together. For example, 30% + 45% = 75%.
Use it to add tax or a tip, raise a price, take off a discount, or grow a score. It works with decimals and negative numbers too. A chart shows the base, the change, and the final result, so you can see how the parts fit together.
How to use our Add Percentage Calculator
Pick a mode, type your numbers, and the calculator shows the answer, the percentage amount, step-by-step math, and a bar chart.
Calculation Mode: Choose "Base + %" to add or subtract a percent from a number. Choose "% + %" to add two percentages together.
Base Value: Type the starting number, like a price or total. Negative numbers are fine.
Operator button (+ or −): Click the middle button to switch between adding the percent and taking it away.
Percentage Value: Type the percent you want to apply to the base value, such as 15 for 15%.
First Percentage: In "% + %" mode, type the first percent you want to combine.
Second Percentage: In "% + %" mode, type the second percent. The tool adds both and shows the total percent.
Calculate: Results update as you type, but you can click Calculate to refresh them.
Reset to Defaults: Click this to clear your numbers and start over with the sample values.
Adding a Percentage to a Number
Adding a percentage means you take part of a number and then put that part back onto the number. A percent is just a part out of 100. So 15% means 15 out of every 100, or 0.15 as a decimal.
The Formula
To add a percent to a base value:
- Percent amount = base × (percent ÷ 100)
- Result = base + percent amount
You can also do it in one step: Result = base × (1 + percent ÷ 100)
Example
Add 15% to 200. First, 15 ÷ 100 = 0.15. Then 200 × 0.15 = 30. Last, 200 + 30 = 230. The one-step way gives the same answer: 200 × 1.15 = 230.
Subtracting a Percentage
Taking a percent off works the same way, but you subtract at the end. Take 15% off 200: 200 − 30 = 170. In one step, 200 × 0.85 = 170.
Adding Two Percentages Together
When you add two percents that both come from the same base, you can just add the numbers. For example, 30% + 45% = 75%. As a decimal, that is 0.75.
Careful: this only works if both percents are of the same starting number. If one percent is taken after the other changes the number, like a 30% raise followed by a 45% raise, the percents do not simply add. That is called a compound change, and the answer is bigger than 75%.
Where You Use This
- Tax: add sales tax to a price.
- Tips: add 18% or 20% to a restaurant bill.
- Sales: take 25% off a sticker price, or set a selling price.
- Pay: add a percent raise to a salary.
- Growth: add a percent increase to sales, weight, or scores.
Common Mistakes
Do not add the percent number straight to the base. Adding 15% to 200 is not 215. You must find 15% of 200 first, which is 30.
Also watch the base. A 10% increase and then a 10% decrease does not bring you back to the start. 100 grows to 110, then drops to 99. The second percent uses a bigger base, so the two changes do not cancel out. To compare two values fairly, the Percent Difference Calculator and Percent Error Calculator use a shared reference instead.