Summary

To decrease a number by a specific percentage, you can use a formula that multiplies the number by 1 minus the percentage. In the example shown, the formula in cell E5 is:

=C5*(1-D5)

The results in column E are decimal values with the percentage number format applied.

Generic formula

=number*(1-percent)

Explanation 

In this example, the goal is to decrease the prices shown in column C by the percentages shown in column D. For example, given an original price of $70.00, and an decrease of 10% ($7.00), the result should be $63.00. The general formula for this calculation, where "x" is the new price, is:

x=old*(1-percentage)
x=70*(1-10%)
x=70*0.90
x=63.00

Converting this to an Excel formula with cell references, the formula in E5 becomes:

=C5*(1-D5)
=70*(1-0.1)
=70*0.9
=63.00

As the formula is copied down, the formula returns a new price for each item in the table, based on the percentages shown in column D.

Negative percentages

A negative percentage will have the effect of increasing the original price. For example, with -10% in cell D5 (-0.10), the formula evaluates like this:

=C5*(1-D5)
=70*(1--0.1)
=70*1.10
=77.00

This example explains the general formula for increasing a number by a given percentage.

Formatting percentages in Excel

In mathematics, a percentage is a number expressed as a fraction of 100. For example, 95% is read as "Ninety-five percent" and is equivalent to 95/100 or 0.95. Accordingly, the values in column D are decimal values, with the Percentage number format applied.

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Hi - I'm Dave Bruns, and I run Exceljet with my wife, Lisa. Our goal is to help you work faster in Excel. We create short videos, and clear examples of formulas, functions, pivot tables, conditional formatting, and charts.

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