How to Calculate Reverse Percentage

How to Calculate Reverse Percentage
••• Cameravit/iStock/GettyImages

If you have a starting amount and you want to add a percentage, simply multiply the percent by the original amount to find the amount that gets added. For example, if you need to calculate how much sales tax or tip to add to the bill. But if you only have the final amount know the percentage added, you need to work in reverse to find the original amount. For example, if you had the final cost and the percentage of sales tax and you want to know the cost before tax.

    Divide the percentage added to the original by 100. For example, if a sales tax of 6 percent was added to the bill to make it $212, work out

    6 ÷ 100 = 0.06

    Add 1 to the percentage expressed as a decimal. In this example,work out

    1 + 0.06 = 1.06

    Divide the final amount by the decimal to find the original amount before the percentage was added. In this example, work out

    212 ÷ 1.06 = 200

    The amount before the sales tax was added is $200.

    Subtract the original amount from the final amount to find the amount added. In this example, work out

    212 - 200 = 12

    You now know that $12 was added.

Related Articles

How to Calculate 20% Off
How to Add Percentage to a Price
How to Calculate Percent Decline
How to Calculate Percent of Return
How to Subtract Percentages
How to Calculate Shrinkage Percentage
How to Calculate Cost Increase by a Percent
How to Increase a Number by a Percentage
How to Calculate a 20 Percent Markup
How to Calculate Percent Off
How to Make a Five Percent Solution With Salt
How to Calculate Percentage Decrease on a Calculator
How to Figure Out Percentages
How to Calculate the Percentage of a Number
How to Calculate Rate of Decrease
How to Subtract 20% on a Calculator
How to Dissolve Magnesium Chloride
How to Calculate Weighted Class Grades
How to Calculate Percentage Reduction