Prevent Duplicate Data Entry using Cell Validations

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We all know that data validation is a very useful feature in Excel. You can use data validation to create a drop-down list in a cell and limit the values user can enter. But, do you know that you can use data validation in a multitude of ways to prevent users from entering wrong data?

Here is a practical application: Prevent users from entering duplicate values in a range of cells.

For eg. you are making an invoice. Wouldn’t it be cool if Excel prompted you when you enter a duplicate line item so that increase the item quantity instead of repeating it.

Here is a 3 step tutorial to do just that.

Step 1: Identify the range of cells where you want only unique values to be entered

This is simple. All you have to do is find the range where you want to control the user input. Lets say the range is B4:B11

Step 2: Set up Data Validation to prevent duplicate entries

Select the range (B4:B11) and go to data validation (Excel 2007: Data Ribbon > Data Validation, or press ALT+AVV)

Using Data Validation to prevent DuplicatesNow, specify the validation type as “Custom”, this will allow us to use formulas to check for valid data. In our case, we need check if a particular entry is duplicated in the range B4:B11. This can be easily done using COUNTIF formula [learn COUNTIF Formula in plain English].

Go to the formula field and type the countif formula like this: =COUNTIF($B$4:$B$11,B4)<=1

Also, you can set up the “Error Alert” so that you can show a custom message when a duplicate value is typed, like “You have already added that product” message.

Data Validation - Error message

Once you set up error message, it will show up like this:

Data validation to prevent duplicates - error message example
Step 3: Sit back and Relax

The third step is all too familiar. Now that you have prevented duplicate entries in your spreadsheets you can sit back and relax. May be read a few more spreadcheats.

More kickass stuff on data validation (and working with duplicates) using excel

There are a ton of useful articles on the site related to data validation and working with duplicates using excel. Here is a sample. Get started and learn something useful today.

This post is part of our spreadcheats series (yes, the series is still going after one year 😛 )

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13 Responses to “Convert fractional Excel time to hours & minutes [Quick tip]”

  1. Debraj Roy says:

    Hi Purna..

    Again a great tip.. Its a great way to convert Fractional Time..
    By the way.. Excel has two great and rarely used formula..

    =DOLLARFR(7.8,60) and =DOLLARDE(7.48,60)

    basically US Account person uses those to convert some currency denomination.. and we can use it to convert Year(i.e 3.11 Year = 3 year 11 month) and Week(6.5 week = 6 week 5 days), in the same manner...

  2. Jason says:

    This doesn't work for me. When applying the custom format of [h]:mm to 7.8 I get 187:12

    Any ideas why?

    • Hui... says:

      @Jason
      7.8 in Excel talk means 7.8 days
      =7.8*24
      =187.2 Hrs
      =187 Hrs 12 Mins

      If you follow Chandoo's instructions you will see that he divides the 7.8 by 24 to get it to a fraction of a day

      Simple, assuming the fractional time is in cell A1,

      Use below steps to convert it to hours & minutes:

      1. In the target cell, write =A1/24
      2. Select the target cell and press CTRL+1 to format it (you can also right click and select format cells)
      3. Select Custom from “Number” tab and enter the code [h]:mm
      4. Done!

  3. WhoKnows says:

    Hi, sorry to point this out but Column C Header is misspelt 'Hours Palyed'

  4. abhishek malik says:

    good one

  5. Julia says:

    So how do I go the other way and get hours and minutes to fractional time?

    • Chandoo says:

      If you have 7.5 in cell A1,

      - Use int(A1) to get the hours.
      - Use mod(A1,1)*60 to get minutes.

      If you have 7:30 (formatted as time) in A1

      - Use hours(a1) to get hours
      - Use minutes(a1) to get minutes.

      • Paula says:

        I had the same issue. You can solve it by changing the format as described above:

        Right click cell > Format Cells > (In Number tab) > Custom > Then enter the code [h]:mm
        ([hh]:mm and [hhh]:mm are nice too if you want to show leading zeros)

        • Jack Scarce says:

          Thanks guys, these are the tips I'm looking for.
          ...dividing the number of minutes elapsed by the percent change is my task - "int" is the key this time

  6. Srikanth says:

    It doesnt work for greater than 24 hours
    It returns 1:30 for 25.5 hours. It should have returned 25:30

    Ideally I would right function as
    =QUOTIENT(A1,1)&":"&MOD(A1,1)*60

    • Paula says:

      Sorry, replied to wrong comment....

      ----
      I had the same issue. You can solve it by changing the format as described above:

      Right click cell > Format Cells > (In Number tab) > Custom > Then enter the code [h]:mm
      ([hh]:mm and [hhh]:mm are nice too if you want to show leading zeros)

  7. Daniel says:

    Clever use of MOD here to extract the decimal part of a number. Divide a number containing a decimal by 1 and return the remainder. Humm. Very clever.

  8. Tomer says:

    Thanks very much, extremely useful !

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