PERCENTILE.INC Function
Basic Description
The Excel PERCENTILE.INC function returns the k’th percentile of a supplied range of values for a given value of k, within the range 0 to 1 (inclusive). The function is new in Excel 2010 and so is not available in earlier versions of Excel. However, Percentile.Inc is simply a renamed version of the old Percentile function, that is available in earlier versions of Excel.
Syntax: PERCENTILE.INC( array, k )
Where the function arguments are:
array  –  The range of data values for which you want to calculate the k’th percentile 
k  –  The value, between 0 and 1 (inclusive), of the required percentile 
If k is not a multiple of 1/(n1), (where n is the number of values in the supplied array), the function interpolates between the values in the supplied array, to calculate the percentile value.
Percentile.Inc Function Examples
The spreadsheets below show examples of the Excel Percentile.Inc function used to calculate the k’th percentile of a set of values in cells A1 – A6 of the sample spreadsheet, for different values of k. 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 above examples:
 The value of k can be input as a decimal or a percentage – for example, value 0.2 in cell B1, is the same as 20%, – the 20th percentile
 The 50th percentile (see cell B3) falls halfway between the values of 2 and 3. Therefore, in this case, Excel has interpolated, to calculate the result 2.5.
 Similarly, the 95th percentile (see cell B4) falls 75% of the way between 4 and 5. Therefore, in this case, Excel has interpolated, to calculate the result 4.75.
Percentile.Inc Function Errors
If you get an error from the Excel Percentile.Inc function this is likely to be one of the following:
#NUM! – Occurs if either the supplied value of k is is < 0 or > 1 or the supplied array is empty
#VALUE! – Occurs if the supplied value of k is nonnumeric