In Excel 2010, the PERCENTILE function has been replaced by the Percentile.Inc function.
Although it has been replaced, the Percentile function is still available in current versions of Excel (stored in the list of compatibility functions), to allow compatibility with earlier versions of Excel.
However, the Percentile function may not be available in future versions of Excel, so it is advised that you use the Percentile.Inc function if possible.
The Excel Percentile function returns the k'th percentile (i.e. the value below which k% of the data values fall) for a supplied range of values and a supplied k.
The syntax of the function is:
Where the function arguments are:
array    The array of data values for which you want to calculate the k'th percentile. 
k    The value (between 0 and 1) of the required percentile. 
Column B of the spreadsheet below shows four examples of the Excel Percentile function, used to calculate the k'th percentile of the set of values in cells A1A6. In each case, a different value of k is specified.
Formulas:

Results:

Note that in the above examples:
See the Microsoft Office website for further examples of the Excel Percentile function.
If you get an error from the Excel Percentile function this is likely to be one of the following:
#NUM!   
Occurs if either:

#VALUE!    Occurs if the supplied value of k is nonnumeric. 