In Excel 2010, the PERCENTRANK function has been renamed the PERCENTRANK.INC function.
Although it has been replaced, the Percentrank function is still available in Excel 2010 (stored in the list of compatibility functions), to allow compatibility with earlier versions of Excel.
The Excel PERCENTRANK function calculates the relative position of a specified value, within a set of values, as a percentage.
The format of the function is :
Where the function arguments are listed in the table below :
array    The array of values, within which you want to find the relative position of a specific value 
x    The specific value that you want to calculate the relative position of (x must be within the range of the values in the supplied array, but it does not need to be exactly equal to one of the values  if x is not found in the array, the array values are interpolated to calculate the percentage rank) 
[significance]    An optional argument that specifies the number of significant digits that the returned percentage value is rounded to (By default the returned percentage value is accurate to 3 significant digits) 
Cells B1B4 of the spreadsheet below show examples of the Excel Percentrank Function, all of which are used to calculate the relative position of a specific value, within the array of values in cells A1A9.
The formulas for the functions are shown in the spreadsheet on the left, and the results are shown in the spreadsheet on the right.
Formulas:  Results: 
Note that, in the example in cell B2 of the spreadsheet above, the function interpolates one third of the way between the percentrank for 6.5 (=37.5%) and the percentrank for 8 (=50.0%). The resulting value, 41.6666666666667% is rounded down to 5 significant figures, as specified by the supplied [significance] argument.
Further examples of the Excel Percentrank function can be found on the Microsoft Office website
If you get an error from the Excel Percentrank function this is likely to be one of the following:
#N/A    Occurs if the supplied x is smaller than the minimum, or greater than the maximum value in the supplied array.  
#NUM!   

Also, the following formatting problem is encountered by some users:
If the result of your Percentrank function is presented as a decimal, or shows 0%, this is likely to be due to the formatting of the cell containing the function.
This can therefore be fixed by formatting the cell as a percentage, with decimal places :