INDEX function
Returns a value or the reference to a value from within a table or range. There are two forms of the INDEX function: the array form and the reference form.
If you want to 
Then see 
Return the value of a specified cell or array of cells 

Return a reference to specified cells 
Array form
Returns the value of an element in a table or an array, selected by the row and column number indexes.
Use the array form if the first argument to INDEX is an array constant.
INDEX(array,row_num,column_num)
Array is a range of cells or an array constant.

If array contains only one row or column, the corresponding row_num or column_num argument is optional.

If array has more than one row and more than one column, and only row_num or column_num is used, INDEX returns an array of the entire row or column in array.
Row_num selects the row in array from which to return a value. If row_num is omitted, column_num is required.
Column_num selects the column in array from which to return a value. If column_num is omitted, row_num is required.
Remarks

If both the row_num and column_num arguments are used, INDEX returns the value in the cell at the intersection of row_num and column_num.

If you set row_num or column_num to 0 (zero), INDEX returns the array of values for the entire column or row, respectively. To use values returned as an array, enter the INDEX function as an array formula in a horizontal range of cells for a row, and in a vertical range of cells for a column. To enter an array formula, press CTRL+SHIFT+ENTER.

Row_num and column_num must point to a cell within array; otherwise, INDEX returns the #REF! error value.
Example 1
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example

Create a blank workbook or worksheet.

Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In the worksheet, select cell A1, and press CTRL+V.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.


Example 2
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example

Create a blank workbook or worksheet.

Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In the worksheet, select cell A1, and press CTRL+V.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.


Note The formula in the example must be entered as an array formula. After copying the example to a blank worksheet, select the range A2:A3 starting with the formula cell. Press F2, and then press CTRL+SHIFT+ENTER. If the formula is not entered as an array formula, the single result is 2.
Reference form
Returns the reference of the cell at the intersection of a particular row and column. If the reference is made up of nonadjacent selections, you can pick the selection to look in.
INDEX(reference,row_num,column_num,area_num)
Reference is a reference to one or more cell ranges.

If you are entering a nonadjacent range for the reference, enclose reference in parentheses.

If each area in reference contains only one row or column, the row_num or column_num argument, respectively, is optional. For example, for a single row reference, use INDEX(reference,,column_num).
Row_num is the number of the row in reference from which to return a reference.
Column_num is the number of the column in reference from which to return a reference.
Area_num selects a range in reference from which to return the intersection of row_num and column_num. The first area selected or entered is numbered 1, the second is 2, and so on. If area_num is omitted, INDEX uses area 1.

For example, if reference describes the cells (A1:B4,D1:E4,G1:H4), then area_num 1 is the range A1:B4, area_num 2 is the range D1:E4, and area_num 3 is the range G1:H4.
Remarks

After reference and area_num have selected a particular range, row_num and column_num select a particular cell: row_num 1 is the first row in the range, column_num 1 is the first column, and so on. The reference returned by INDEX is the intersection of row_num and column_num.

If you set row_num or column_num to 0 (zero), INDEX returns the reference for the entire column or row, respectively.

Row_num, column_num, and area_num must point to a cell within reference; otherwise, INDEX returns the #REF! error value. If row_num and column_num are omitted, INDEX returns the area in reference specified by area_num.

The result of the INDEX function is a reference and is interpreted as such by other formulas. Depending on the formula, the return value of INDEX may be used as a reference or as a value. For example, the formula CELL("width",INDEX(A1:B2,1,2)) is equivalent to CELL("width",B1). The CELL function uses the return value of INDEX as a cell reference. On the other hand, a formula such as 2*INDEX(A1:B2,1,2) translates the return value of INDEX into the number in cell B1.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example

Create a blank workbook or worksheet.

Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In the worksheet, select cell A1, and press CTRL+V.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

