How to auto number a column in Excel?
Have you ever wanted to number a column in Excel? This tutorial will talk about some methods for numbering a column.
Auto number a column by formula =ROW()
Auto number a column by formula =OFFSET()
Auto number a column by Auto Fill Handle
Number a column by Insert Sequence Number of Kutools for Excel
Auto number a column by formula =ROW()
If you want to number the column based on the row numbers, you can type this formula =ROW() into a cell and press Enter key then drag the autofill handle to the cells you need to number.
Auto number a column by formula =OFFSET(A2,1,0)+1
If you want to auto number the column cells not based on the row number, you can type this formula =OFFSET(A2,1,0)+1 into Cell A2 which you want to begin the number series from 1, and press Enter key then drag the autofill handle to cells you need.
Note:
1. With above formula to auto number a column, A2 is current cell's address, and the cell above this cell must be blank or 0. For example, if you want to enter this formula into Cell K5, the formula should be modified to =OFFSET(K5,1,0)+1, and the Cell K4 must be blank or 0.
2. If you remove one number from the number series, the below numbers will be start from 1 again.
Insert Sequnce Number in Excel 
If you want to insert customized sequential numbers in Excel, such as KTE0001Jone, KTE0002Jone, KTE0003Jone..., the sequence strings will not be filled normally when dragging the mouse in Excel. Now, with the Insert Sequence Number utility of Kutools for Excel, you can create any customizing sequence numbers and insert them quickly. Click to download 30day free trial. 
Auto number a column by AutoFill function
In Excel, AutoFill function also can help you to number a column.
Type 1 into a cell that you want to start the numbering, then drag the autofill handle at the rightdown corner of the cell to the cells you want to number, and click the fill options to expand the option, and check Fill Series, then the cells are numbered. See screenshot.
Note: If you delete one number of the number series, the other numbers are kept.
Insert column number by Insert Sequence Number of Kutools for Excel
If you want to insert custom sequence number to number a column, you can try the Insert Sequence Number tool of Kutools for Excel.
Kutools for Excel, with more than 300 handy functions, makes your jobs more easier.  
After free installing Kutools for Excel, please do as below:
1. Click Kutools > Insert > Insert Sequence Number.
2. Click New button to expand the dialog, then set your custom sequence as you need, you can specify the prefix and suffix, also can define the number of digits you want. See screenshot:
3. Click Add to create this sequence, then select a column range you want to insert the numbers, click Fill Range to fill the numbers into cells.
Tips:
1. In the Insert Sequence Number dialog box, it will mark the last inserted sequential numbers in the Previous list, and if you insert this sequence number at next time, the first sequential number will be marked in Next list.
2. You can click New button to create more sequential numbers.
3. You can click Reset to reset the sequence.
4. With Insert Sequence Number tool, you also can do following operations:
Quickly create and insert repeated sequential numbers in a range of cells
Quickly create and insert sequential numbers in merged cells
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