Write down the percentage or input it into your calculator.
Divide the percentage by 100. A quick way to do this is to simply move the decimal place two positions to the left. If you don't see a decimal in the percentage, assume that the decimal follows the last digit to the right. For example, 80 percent would become 0.80.
Count your percentage in terms of the whole unit through multiplication. For example, if you have a blouse that was $50 and now is 80 percent off, you would use the decimal form 0.80 and multiply this times the original price of 50. When you multiply 50 times 0.80, you get 40. This means that you can count this percentage as $40. If you want to find the new price, subtract the percentage from the original price. In this case, you would subtract $40 from $50 to get a sale price of $10.