How to add unique id number column for duplicate rows in Excel?

Supposing there are some duplicate data in a column, now you want to add unique ID number for these duplicate rows as below screenshot shown, do you have any good ways to add them? Here, I introduce a formula to help you quickly handle this job in Excel.

Adding unique ID number column for duplicate rows with a formula

Adding missing ID number with Kutools for Excel

Adding unique ID number column for duplicate rows with a formula

To add unique ID number for duplicate data, you can do as these steps:

1. type 1 into the cell which is adjacent to the first data you want to add ID number.

2. Then in the cell below it, type this formula =IF(B1=B2,A1,A1+1), press Enter key to get the first result, drag fill handle down until last data showing up.

In the formula, B1, B2 are the first two cells in the duplicate data column, A1 is the first ID cell.

Adding missing ID number with Kutools for Excel

If you have a list of ID numbers which including some missing numbers as below screenshot shown, you can apply Kutools for Excel’s Find Missing Sequence Number utility to quickly find and add the missing number.

After installing Kutools for Excel, please do as below:

1. Select the ID numbers you want to insert missing numbers, click Kutools > Insert > Find Missing Sequence Number.

2. In the popping dialog, you can choose one option to add or highlight missing numbers as you need.

3. Click Ok. A dialog pops out to remind you the number of missing data, close it. Then all missing numbers have been added or highlighted in the column or beside the column.

Add missing numbers	Find the missing rows