The percent key on a calculator is used to calculate percentages. For example, to calculate 15% of 100, you would enter 15 % 100 =. The answer, 15, would be displayed on the screen.
The percent key can also be used to calculate discounts and markups. For example, if a shirt is originally priced at $20 and is on sale for 15% off, you would enter 20 * 15 % =. The answer, 3, would be the discount amount. To calculate the sale price, you would subtract the discount amount from the original price: 20 – 3 = 17.