Calculate Percent Difference

Percent difference between two numbers is nothing but the difference between them expressed as a percent change with respect to the numbers. It is generally used to compare two different values of the same property. When you are asked to find the budget increase from quarter to quarter, or the population growth over a period of 10 years, you are expected to calculate percent difference between the two values. Scientists often use percent difference while comparing two calculated values of a particular experiment.

How to Calculate Percent Difference?
Percent difference is similar to another term known as percent error. The only difference between the two is that percent error measures the difference between an accepted value and an observed value, whereas, neither of the values used in the calculation of percent difference are the accepted ones. Both are experimental values describing the same characteristic or property. Given below is the formula for calculating percent difference between two observed values.

Percent Difference = { ( |Value 1 - Value 2| ) / [ (Value 1+ Value 2) / 2 ] } X 100

Here, as none of the values are actual or accepted, the absolute difference between them has to be divided by the average value that is obtained by taking the mean of the two given values. It is very important that both the values that are to be compared should have the same units. Another important thing to remember, is that the difference calculated (|Value 1 - Value 2|), is the absolute difference, that is you have to take the modulus of the difference. Let us take an example.

If we are asked to find the percent difference between the numbers 24 and 20. This is how to go about it:

Absolute difference = |24 - 20| = 4
Average value = (24 + 20) / 2 = 22
Percent difference = (4 / 22) X 100 = 18.18%

Now, if one of the values is an accepted value, the formula to find percent difference becomes the same as that used to calculate percent error.

Percent Difference = [ ( |Value 1 - Value 2| ) / Value 2 ] X 100

where, Value 1 = observed or calculated value
Value 2 = exact or accepted value

For example, if you have to calculate percent change between two values, where the exact value is 20 and the calculated value is 24, this is how you do it:

Absolute difference = |24 - 20| = 4
Percent difference = (4 / 20) X 100 = 20%

Calculating Percent Difference in Excel
There is no built-in function in Excel to calculate percent difference or percent change. So, if you are working on an Excel sheet and you need to find the percent difference between two numbers, this is how you could calculate percentage increase or decrease.

If your values are listed in the A1 and A2 cells of an excel spreadsheet, you can find the percent difference by using the given formula. Just apply the given formula in the input line and click on the cell where you want your answer to appear in.

Percent Difference = ((A2-A1)/A1)*100

To get the value in the percentage figure, you need to click on the % icon on the formatting toolbar on the top of the page.

Well, I hope you will be able to calculate the percent difference between two numbers, using the methods given in the article. Mathematics can be extremely simple if you remember the right formulas and solve the problems systematically. So, go ahead, have fun with the numbers!