The area between two curves is the sum of the absolute value of their differences, multiplied by the spacing between measurement points. In business, calculating the area between two curves can give you a measure of the overall difference between two time series, such as profit, costs or sales. Microsoft Excel can manipulate data to calculate the area between two data series using only basic functions.

Launch Microsoft Excel and load a worksheet containing the data for the two curves you want to measure the area between. The two data series need to be on the same basis of time or space. That means you need to have a corresponding data value for curves A and B for each evenly spaced measurement point.

Select an empty column and label it "Absolute Difference" or "|A - B|." Enter the following formula into the Excel formula box:

\= ABS(A$1 - B$1)

This formula calculates the absolute value of the difference between the curves. The absolute value is used because area cannot be negative.

Select an empty cell and label it "Sum of Difference." Enter the following formula into the Excel formula box:

\= SUM(C1:C100)

Replace "C1:C100" with the range of the data in your "Absolute Difference" column. This will calculate a single sum for the column.

Multiple the value of the "Sum of Difference" cell by the spacing between data values to obtain the final area. For example, if data were spaced every one week or one month, no calculation is needed. You would multiple by three if you calculated a value for every third day.

Tip

The units of the area may be something unusual like dollar weeks. Compare the magnitude of the areas between different curves

Warning

The instructions in this article apply to Excel 2010. Other versions may contain significant differences.