How to prevent duplicates in a column in Excel

Today I'll tell you how to prevent duplicates from appearing in a column of your Excel worksheet. This tip works in Microsoft Excel 2016, 2013, 2010 and lower.

We covered a similar topic in one of our previous articles. So you should know how to automatically highlight duplicates in Excel once something has been typed.

This article will help you stop duplicates appearing in one or several columns in your Excel worksheet. So you can have only unique data in the 1st column of your table be there invoice numbers, stock keeping units, or dates, each mentioned only once.

How to stop duplication - 5 easy steps

Excel has Data Validation - one unfairly forgotten tool. With its help you can avoid errors occurring in your records. We will be sure to devote some future articles to this helpful feature. And now, as a warm-up, you will see a simple example of using this option. :)

Suppose, you have a worksheet named "Customers" that includes such columns as Names, Phone numbers, and Emails you use for sending newsletters. Thus all email addresses must be unique. Follow the steps below to avoid sending the same message to one client twice.

Table withous duplicates. All email addresses must be unique

  1. If necessary, find and delete all duplicates from the table. You can first highlight the dupes and delete them manually after looking through the values. Or you can remove all duplicates with the help of the Duplicate Remover add-in.
  2. Select the entire column where you need to avoid duplicates. Click on the first cell with data keeping the Shift keyboard button pressed and then select the last cell. Or simply use the combination of Ctrl + Shift + End. It is important to select the 1st data cell first.
     Select the entire column where you need to avoid duplicates

    Note: If your data are in a simple Excel range as opposed to a full-fledged Excel table, you need to select all the cells in your column, even the blank ones, from D2 to D1048576
     Select all the cells in your column
  3. Go to Excel "Data" tab and click on the Data Validation icon to open the dialog box.
     Go to Excel
  4. On the Settings tab, choose "Custom" from the Allow drop down list and enter =COUNTIF($D:$D,D2)=1 into the Formula box.
    Formula to count duplicate entries in a column

    Here $D:$D are the addresses of the first and the last cells in your column. Please pay attention to the dollar signs that are used to indicate absolute reference. D2 is the address of the first selected cell, it is not an absolute reference.

    With the help of this formula Excel counts the number of occurrences of the D2 value in the range D1:D1048576. If it is mentioned just once, then everything is fine. When the same value appears several times, Excel will show an alert message with the text you specify on the "Error alert" tab.

    Tip: You can compare your column with another column to find duplicates. The second column can be on a different worksheet or event workbook. For example, you can compare the current column with the one that contains the blacklisted emails of customers
    you don't won't to work with any longer. :) I will give more details about this Data Validation option in one of my future posts.
  5. Switch to the "Error alert" tab, and enter your text into the fields Title and Error message. Excel will show you this text as soon as you try to enter a duplicate entry into the column. Try to type the details that will be accurate and clear for you or your colleagues. Otherwise, in a month or so you can forget what it means.

    For example:
    Title: "Duplicate email entry"
    Message: "You have entered an email address that already exists in this column. Only unique emails are allowed."
    Only unique emails are allowed.

  6. Click OK to close the "Data validation" dialog.

    Now when you try to paste an address that already exists in the column, you will see an error message with your text. The rule will work both if you enter a new address into an empty cell for a new customer and if you try to replace an email for the existing client:
    Duplicate entry error

If your "No duplicates allowed" rule can have exceptions :)

On the fourth step choose Warning or Information from the Style menu list. The alert message behavior will change correspondingly:

Warning: The buttons on the dialog will turn as Yes / No / Cancel. If you click Yes, the value you enter will be added. Press No or Cancel to get back to editing the cell. No is the default button.
Data validation: Warning style

Information: The buttons on the alert message will be Ok and Cancel. If you click Ok (the default one), a duplicate will be added. Cancel will take you back to the editing mode.
Information about new duplicate entry

Note: I'd like to pay your attention again to the fact that the alert about a duplicate entry will appear only when you try to enter a value into a cell. Excel will not find existing duplicates when you configure the Data Validation tool. It will not happen even if there are more than 150 dupes in your column. :).

86 Responses to "How to prevent duplicates in a column in Excel"

  1. Ahmad Al-Musallami says:

    Thanks for the nice tip...

    I published it on our Excel group for hoping more members will benefit from

    http://www.linkedin.com/groupItem?view=&gid=153811&type=member&item=5798383424137875460&trk=groups%2Finclude%2Fitem_snippet-0-b-ttl

    Regards,
    Ahmad

  2. Kriti says:

    This does not work for simple text or string values.

    any suggestions?

  3. Anonymous says:

    alex, I emailed you.

    Thanks,
    Niall Williams

  4. Rina says:

    The steps wont work in my excel sheet. I cant enter value in the cell, the alert keep prompting. Even though, the value is a new value, not duplicating any value.
    I use Excel 2007. The data is a combination of characters. E.g. TA001, PB056.
    Pls help.

  5. ken says:

    Doesn't seem to work if the data column to be checked for duplicates is populated via a linked combo box, or other formula. Is there a way around this?

  6. Sian-ann says:

    This doesn't work if you copy and paste the value?? How do I change this?

    • Alexander says:

      Unfortunately, Data Validation prevents invalid entries only when you type data directly in a cell using the keyboard. The pasted values are not checked for validity.

      If you want to block the insertion of values which are already in the list from the clipboard, a special VBA code is needed. You can ask for a macro on http://www.mrexcel.com or http://www.excelforum.com forums.

      Please note that a quite complex code will be required to process all the variants.

  7. Leng says:

    I have a question, would appreciate if you could help. I am applying the rule to a list of names, however, it doesn't recognise the entire content of the cell ie, if I already have an Adam Smith in my list and I would like to add Adam Jones, it recognises 'Adam' and will prompt an error. Would you be able to advise?

    Thanks!

  8. Leng says:

    What if I already have a "data validation" for a list in that column, but still need to prevent duplicates, how do I fix it ?

    Is there another way without using Data Validation ?

  9. pradeep Kumar says:

    How to prevent duplicate numeric and text entries in excel column, only unique numeric and text data allowed. above formula: example =countif($D:$D,D2)=1 is working for both numeric and text value to prevent duplicate.
    My question are below:
    1. How to prevent duplicate only Numeric entries in excel column, only Unique Numeric data allowed.
    2. As well as how to prevent duplicate only text entries in excel column, only Unique text data allowed.

    Kindly do the reply needful.

    Regards
    Pradeep Kumar

    • Alexander says:

      Please specify what result you want to get. This formula works for text as well as for numeric data.

      If you want to allow only unique numbers, text can be repeated, then use this formula:
      =OR(ISNUMBER(D2)=FALSE, countif($D:$D,D2)=1)

      If only unique text is allowed (numbers can duplicate), then the formula will be as follows:
      =OR(ISNUMBER(D2)=TRUE, countif($D:$D,D2)=1)

      If you want to get something different, please give me more details.

      • Sanjay Joshi says:

        Dear,

        Your trick is nice but i m facing problem that if somebody use cut copy paste the trick is gonna fail.

      • DEVIDAS says:

        It is working with this formula =OR(ISNUMBER(D2)=TRUE, countif($D:$D,D2)=1) in excel 2010. thank you.

      • aizat says:

        f you want to allow only unique numbers, text can be repeated, then use this formula:
        =OR(ISNUMBER(D2)=FALSE, countif($D:$D,D2)=1)

        hi, i still can;t get it going with this formula.

  10. Sanhita says:

    Hi ,

    I have a series of web URLS in an excel . I want the duplicates to be stopped from being entered . Could you tell me how to do that ..

  11. Aki says:

    yes correct but still remain same problem using with copy-paste,
    how to useful with copy-paste?

  12. Joanna says:

    Is day a way to prevent similar entries? What I mean is, I would like an alert to appear if a part of it already appeared before. For example:
    I have a table with product specification:
    1. coolproduct 17B
    2. thing 19C
    3. whatever 120

    Is there a way for an alert to pop up if I put in "coolproduct 19A" and suggest that a similar entry already exists?

  13. Reece says:

    After you've removed the duplicates, if you want to send an email to the list, the emails must be comma separated. You can turn a column into a list using this in-browser tool:
    http://convert.town/column-to-comma-separated-list

  14. Dave says:

    What is the best way to do the following;
    allocating employees to vehicles lets say vehicle number 51. If 51 is selected for more than 4 employees to go to a site an error is generated to say to the user to select another vehicle as this one is full

  15. Aisha says:

    Thank you.
    This was exactly what I was looking for.
    Saved me a lot of manual time and effort.

    Simple and easy to understand steps for a novice like myself.

  16. Kev says:

    I want the whole of the A columns to restrict duplications and have put in the following formula but it does not seem to be working:-
    =COUNTIF($A:$A,A1)=1

    Is this wrong?

  17. Kev says:

    I am inputting just a straight number i.e. 1150600542
    as an example number so nothing irregular.

  18. Supi says:

    How to avoid duplicate entry in multiple column.
    For Example:

    COL_A COL_B COL_C COMMENT
    JOB_A 1 2 Data is ok
    JOB_B 1 2 ok Although there are duplicate data in COL_B and COL_C
    COL_A 1 1 ok Although there are duplicate data in COL_A and COL_B
    JOB_A 1 2 NOT OK because exacly similar data is there in the first raw.

  19. http://www.indiatoppackers.in/ says:

    You provide very good tutorial. thanks.

  20. http://www.indiatoppackers.in/ says:

    nice toturial.

  21. http://www.indiatoppackers.in/ says:

    list of top packers and movers in delhi

  22. A.V.R. MURTY says:

    I have a similar problem but with multiple criteria. How to identify an entry in an active cell is duplicate or not based on dual matching criteria?

    Regards,
    A.V.R. Murty

  23. SODwyer says:

    Hi. I havea concatenate formula where I want an error to be shown when there are duplicates in the column. This doesn't seem to work.
    Sean

  24. MANPREET says:

    This has helped me a lot. I have a combination of data in 2 columns which must be unique.

    Example of valid data
    Date | Shift
    08 Aug | Night
    08 Aug | Day

    Example of INVALID data
    Date | Shift
    08 Aug | Night
    08 Aug | Night

    So I have to avoid entry of duplicate data in a combination of columns. I am not able to figure it out please help.

  25. Deepak says:

    It is not working in my excel sheet. please Help me..

  26. shiny says:

    It did not work at first but after I unchecked the "ignore blank" box next to custom it worked. Very helpful. Thank you.

  27. Grace says:

    I am encoding tons of household ID nos which consists 10 digits-4 digits-5digits. I have to ensure that no repetition of the said HH No. The formula is working just fine. However, when I Copy/Paste the whole HH ID No., the formula is NOT working. Any other way that whenever I copy/paste I get the same result of the used formula? Thank you.

  28. me says:

    thnx, it war really helpfull!

  29. Junaid says:

    how can i assign two validation on a single cell
    one is for list validation (means the data should be from that range)
    second i want to prevent them from repetition

    how can i do this ?
    P7 to P506 have GR# which are for list
    i want to prevent C column to not to repeat and should be from the P column

  30. ahmed ibrahim says:

    It works for a new file created "email" colum with "UNIQUE" formula.

    I couldn't implement it to an existing file's "email" field after removing duplicates, wanted to convert it's email colum into a unique field, but didn't function.!

    Thanking you,,!

    AHMED IBRAHIM
    DUBAI L,,,

  31. Surya says:

    Input
    Column A Column B
    Grapes Fruits
    Grapes Fruits
    Tomatto Vegetable
    Apple Fruits
    Onion Vegetable
    Tomatto Vegetable
    Apple Fruits
    Mango Fruits
    Papaya Fruits

    Output
    Fruits 4
    Vegetable 2
    Anybody know the answers.

  32. Zabih says:

    Suppose I want this formula to affect the value in the middle of a column up to a certain point. e.g. from D5577 to D10000. Because I already have some data in that column and want the formula to ignore that data.

  33. Banashree Pattanayak says:

    Hi,

    I am trying to prevent duplicacy by data validation but it is not applicable in case of copy-pase option. what i mean to say is when i copy the cell value and paste somewhere else in the same column it does not show the error message. however it shows when i am typing the same value. in this way my purpose is not fulfilled. plz guide in this regard.

    thank you
    banashree

  34. Ray says:

    I would like to stop duplicate value entry in a self generating list. Any idea how to do it.

  35. bhavesh Chauhan says:

    I want to make one table which have no duplicate numbers & also it is random .
    Requirement :
    First input : 1 - 90 for same numbers came in first column
    Second input : 1 -90 random no came in 910 columns but not repeat

  36. Avinash says:

    How do we copy the entire data of my worksheet i'm asking this question because when i select and copy(ctrl+c), it says "That command cannot be used on multiple selections". Please Help

  37. Vavine Pianta says:

    hi,
    i have just tried out this formula to one of my spreed sheet and it's great.
    However, when i type in a new invoice number on the column I've just selected it keeps picking up as duplicate. Also, how do i remove this format to re-set again? please need assistance asap.

    thanks - Vavine Pianta

  38. manjunatha says:

    Hello,

    Im trying to remove the duplicates and duplicates has appear in the next column.

    Example:
    In column A name has the below Alex,Tom,Tej,Alex,Tom,Alex.

    Duplicates has to appear in the B column.

    please help me on this

  39. Jacky Choo says:

    Hi, This is really helpful, would like to check, what if the fields that I wanted to control are already an data validation(drop down) field?

  40. Danish khan says:

    Please helped me a lot. I have a combination of data in 2 different columns which must be unique.

    Example of correct data
    emp id | Date
    101 | 27/05/2016
    101 | 28/05/2016

    Example of Incorrect data
    emp id | Date
    101 | 27/05/2016
    101 | 27/05/2016

    So I want to stop duplicate data in a combination of columns. I am trying to do but fail always. Please help me in this regard i really need for this ....

  41. KUNAL MORE says:

    Hi, Thank you very much for the information above. It is very helpful. I have a specific question for removing the near match duplicates.
    eg. if particular column there are following entries and I want to keep only those with larger data point in the length.

    RSAsVAGIVGADEEAPPAPK
    SAsVAGIVGADEEAPPA
    SsVDDGNINLTDTSTSNK
    SsVDDGnINLTDTST
    sASAAAILEEDDSKDDmEFK
    TFsGIGFNLTEK

    In this case following entries
    RSAsVAGIVGADEEAPPAPK
    SAsVAGIVGADEEAPPA
    are the same but I need to keep RSAsVAGIVGADEEAPPAPK but not SAsVAGIVGADEEAPPA.
    How it can be done for complete column with various entries? same is true with
    SsVDDGNINLTDTSTSNK
    SsVDDGnINLTDTST
    I need to preserve the longer one and remove the shorter.
    Please help me with this.

  42. Sivahari says:

    hi, this is really helpful

  43. Rohan Singh says:

    Hi,

    When i applied Data Validation then it shows some error which says "Name range that you specified can not be found". Can you please help me on this error pls

  44. johara says:

    I tried to do this so many times, i even installed the trim add-on, but it did not work. is there any other way?

  45. Shafiq Ahmad says:

    I am happy after to learn excel command, how to avoid duplicate.
    I am thanks.

  46. SACHIN says:

    NOT WORKING

  47. Sbeam says:

    Hello, Thank you for the tutorial! I read the part where you mentioned you'd be posting another tutorial on how to check duplicate entries within the same worksheet & even another workbook. I was hoping that you had posted the tutorial & could direct me on where to find it.

    Thanks again!

  48. SAM says:

    COPY AND PASTE FIX
    I thought this was going to be perfect for my needs, until I realised this method doesn't work if copy and pasting data.

    Ok, so this isn't a fix, but rather a solution that suited me and may suit others as well.

    I followed the guide at https://www.ablebits.com/office-addins-blog/2013/09/13/auto-highlight-duplicates-excel/

    if the link doesn't show or whatever, it's the article titled: How to automatically highlight duplicates in Excel once something has been typed.

  49. Pat says:

    How to ignore the first character when avoiding duplicates.
    Example:

    A70000011
    B70000011

    Consider this as a duplicate.

    Also, not consider text a duplicate.
    Example:

    A--END--
    B--END--

    This would NOT be considered a duplicate.

    Any ideas?

  50. Pat says:

    Is there a custome formula that would work in data validation for this?

    I've wasted hours so far... Please help!

  51. Mahadeo Jagtap says:

    HI ,

    Could you help me for combine multiple excel ( Car booking data) in one sheet.

    Thanks

  52. DAVID says:

    MUCH EASIER WAY:

    CLICK FILTER ADVANCED BUTTON

    SELECT COLUMN YOU WISH TO APPLY FILTER TO

    CHECK THE BOX LABELED "UNIQUE RECORDS ONLY"

    YOU ARE DONE, BOW THE DUPLICATES ARE ELIMINATED AND YOU CAN EMAIL YOUR PEOPLE

  53. Ben Hager says:

    Am trying to prevent duplicates in a column of cells in our project log sheets. Each entry contains eight characters, with the first five being able to repeat, but the last three must be unique and sequential (i.e. JR157001, KR257002, ST457003, etc). We continue to get the last three duplicated with the first five being different and it throws everything into chaos when 10-15 entries later you duplicate an existing entry, then all outside files (other software) with the incorrect numbers have to be reworked, wasting a lot of time. I have tried COUNTIF and a few others, but there is always something no right with the formulas. Thanks.

  54. Mayne says:

    Hi, how do I avoid duplicate entries on multiple sheets. E.g I have listed invoices by month to month on a different worksheet tab (One excel spreadsheet but each tab has say Jan, Feb). I've applied the rule and it works but I want it to pick up too if there was any duplicate entry from previous months (e.g I'm entering data for Feb and I'd like to pick up if there was any same invoice number already entered in previous months or tabs). Thanks

  55. DEEPAK SHARMA says:

    I have bulk entries in column $b1:$b450 , it also contains repeated text like "AAA" in cells B2, B5, B8, B10 so on.

    Now i want to give Sno in $A1:$A450, but i dont want that Serial number consider the duplicate text contain in other cells, it should treat 1 for all "AAA"

    Let me know the formula

    Thanks

  56. josh says:

    how to validate name field in excel(cell should not accept number or special characters )?

  57. Abdul Baseer says:

    thanks a lot for the explanation but i am a trainer and want to prepare a sheet that highlights the names of the trainees who got the training in past years, so that to avoid duplication in trainings

  58. Zak says:

    Hello,

    It would seem that for this to work, you need to have a range with cells following one another. In my instance, my cells are individual, i.e. there could be 3 rows seperating them. This means that when i select the data for which i want the rule, it comes up as individual cells rather than a range.

    Any help is appreciated.

  59. Louisa says:

    Can this work across tabs? I am trying to prevent duplicate entries being used across 3 separate tabs, all saved in the single file. The cells are the same in each tab (ie. the same column) in each tab if this helps?

  60. Anas says:

    Hi,
    i have a list of data but all are 19 digits.
    Because of this, duplicates are not identified.
    Could you please share with us the solution.

    Thanks
    Anas

  61. Abrar says:

    i want to extract the report where mobile number and DATE are same so dont consider duplicate. only consider duplicate mobile numbers which have different date.

    Date Mobile
    9/18/17 4:09 PM 923005254870
    9/18/17 6:45 PM 923005254870
    9/14/17 6:10 PM 923008435348
    9/14/17 6:29 PM 923008435348
    9/7/17 8:13 PM 923023689646
    9/14/17 6:55 PM 923023689646
    9/9/17 1:00 PM 923032819439
    9/12/17 2:28 PM 923032819439

  62. Jappek says:

    Hi There,
    Minor issue detected.

    For Word/Office 2013 the formula as mentioned in the article is not allowed.
    The seperator between the range and the criteria must be a semicolon, instead of a comma, like this :

    =COUNTIF($D:$D;D2)=1

    Making this minor correction made it finally work for me ;-)

    Thanks

  63. Jappek says:

    CORRECTION

    Hi There,
    Minor issue detected.

    For Excel 2013 the formula as mentioned in the article is not allowed.
    The seperator between the range and the criteria must be a semicolon, instead of a comma, like this :

    =COUNTIF($D:$D;D2)=1

    Making this minor correction made it finally work for me ;-)

    Thanks

  64. Shawn says:

    This worked for me, thanks! One question: When the alert shows up, is there a way to track which cell the duplicate is in? Sometimes we have so many entries that manually looking for it can take a while. Thank you!

  65. laleh says:

    Hi,

    It is not applicable when pasting. why that is so?

    thx

  66. FRED says:

    THANK YOU, IT IS GREAT.

  67. ARUN CHAUHAN says:

    YOUR FORMULA SO GOOD AND WORKING, GET CONNECT WITH YOU

    THANK YOU SO MUCH

  68. Ravi says:

    Thank you alexander

  69. aizat says:

    Strange, everything seems fine. but no dialog box pop u if duplicate value entered.

  70. trinadh says:

    i have excel sheet with contact number this should be duplicate which was repeating again and again

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