To calculate the interquartile range in Microsoft Excel, first enter the values for which you want to calculate the interquartile range in one single column. To calculate the first quartile, select a blank cell, and enter "=QUARTILE(cell 1:cell 2,1)," where cell 1 and cell 2 are the actual cell labels in Excel. To calculate the third quartile, select another blank cell, and enter "=QUARTILE(cell 1:cell 2, 3)." Subtract the value from the first quartile from the third quartile to get your interquartile range.

**Enter your values into Microsoft Excel**Enter all of the values into a single column into Excel. It does not matter which column to choose.

**Calculate the first quartile value**Click on any blank cell in Excel. Enter "=QUARTLE(cell 1:cell 2, 1)." The first quartile value appears in the previously blank cell.

**Calculate the third quartile value**Select the blank cell immediately below the first quartile. Enter "=QUARTILE(cell 1:cell 2, 3)." The third quartile value appears in the previously blank cell.

**Calculate the interquartile range**Subtract the value derived from the first quartile from the value derived from the third quartile. The value from this formula is the interquartile range. The interquartile range represents middle 50 percent of the data set.