Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, Excel in Microsoft 365, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: Developing Reciprocal Conversion Formulas.

Developing Reciprocal Conversion Formulas

Written by Allen Wyatt (last updated January 1, 2022)
This tip applies to Excel 2007, 2010, 2013, 2016, 2019, Excel in Microsoft 365, and 2021


3

Jeremy posed a problem that is based on two cells, A1 and C1. These cells are designed to contain inches and millimeters, respectively. Jeremy wants a way that someone could enter a value in A1 and it would be converted to millimeters in C1. Conversely, they could enter a value in C1 and it would be converted to inches in A1.

Doing the conversion, of course, isn't the real issue. The problem is that if someone enters a value in A1, that value will overwrite any formula that may be in that cell, and mean that any subsequent value entered in cell C1 would not give the required conversion in the previously overwritten A1.

There are a couple of different ways that this could be approached. If you don't mind expanding your worksheet design to include two more cells, those cells could be used strictly for input and cells A1 and C1 could be used strictly for output. One of the input cells could contain the value to be converted and the other could contain the measurement unit of the input value (in or mm, for instance).

Of course, if you want to really limit yourself to two cells, then you will need to resort to using macros to do the actual conversion. You can use a worksheet event that is triggered every time a cell value is changed, and the event handler could check to see if the cell being changed is either A1 or C1. The following macro gives an example of how this could work:

Private Sub Worksheet_Change(ByVal Target As Range)
    Application.EnableEvents = False
    Select Case Target.Address
        Case "$A$1"
            [C1] = [A1] * 25.4
        Case "$C$1"
            [A1] = [C1] / 25.4
    End Select
    Application.EnableEvents = True
End Sub

Note that you don't have to have any formulas in cells A1 or C1; the formulas are in the macro itself. If there is a change in cell A1 (inches are entered by the user), then the value in cell C1 is changed by the macro. Likewise, if there is a change in cell C1 (millimeters are entered by the user), then the value in cell A1 is changed by the macro. A change in any other cell besides A1 or C1 is ignored by the macro.

Note:

If you would like to know how to use the macros described on this page (or on any other page on the ExcelTips sites), I've prepared a special page that includes helpful information. Click here to open that special page in a new browser tab.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (9581) applies to Microsoft Excel 2007, 2010, 2013, 2016, 2019, Excel in Microsoft 365, and 2021. You can find a version of this tip for the older menu interface of Excel here: Developing Reciprocal Conversion Formulas.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He is president of Sharon Parq Associates, a computer and publishing services company. ...

MORE FROM ALLEN

Last Paragraph Line Strung Out Incorrectly

Justifying a paragraph may have undesired effects on the last line of a paragraph. If this occurs with your text, you'll ...

Discover More

Creating a Letterhead Template

Word is often used to write all sorts of letters. You may want to create a template that makes creating your letters ...

Discover More

Maintaining Formatting when Inserting Documents

Word allows you to easily insert the contents of one document into another. Doing so, however, may result in unintended ...

Discover More

Solve Real Business Problems Master business modeling and analysis techniques with Excel and transform data into bottom-line results. This hands-on, scenario-focused guide shows you how to use the latest Excel tools to integrate data from multiple tables. Check out Microsoft Excel 2013 Data Analysis and Business Modeling today!

More ExcelTips (ribbon)

Reversing Integer Values

Do you need to reverse a series of integer values, such as 5 becomes 1, 4 becomes 2, etc.? There are several ways you can ...

Discover More

Last Non-Zero Value in a Row

If you have a lot of values in a single row, you might want to pull the last non-zero value from that row. There are a ...

Discover More

Counting Cells According to Case

Text placed in cells can either be lowercase, uppercase, or a mixture of the two. If you want to count the cells based ...

Discover More
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

View most recent newsletter.

Comments

If you would like to add an image to your comment (not an avatar, but an image to help in making the point of your comment), include the characters [{fig}] (all 7 characters, in the sequence shown) in your comment text. You’ll be prompted to upload your image when you submit the comment. Maximum image size is 6Mpixels. Images larger than 600px wide or 1000px tall will be reduced. Up to three images may be included in a comment. All images are subject to review. Commenting privileges may be curtailed if inappropriate images are posted.

What is 1 + 1?

2022-01-02 09:18:19

Mike

Please ignore my last comment. I have no idea why it did not work before, but I have just tried it again, in a new blank Worksheet, and the macro works just fine.


2022-01-01 13:52:13

Mike

The only way I could get the Macro to work as expected was to de-select 'After pressing Enter, move selection Direction' in Options. The cells were not updating until the input cell was selected again.

Adding some additional lines made it work for me.

Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
Select Case Target.Address
Case "$A$1"
[C1] = [A1] * 25.4
Case "$C$1"
[A1] = [C1] / 25.4
Case "$B$1"
Range("A1").Select
Case "$D$1"
Range("C1").Select
Case "$A$2"
Range("A1").Select
Case "$C$2"
Range("C1").Select
End Select
Application.EnableEvents = True
End Sub


2022-01-01 06:02:09

Kiwerry

Not wanting to use macros, I use the following solution for conversions.
Example, temperatures: Unit1 in cell D3, unit 2 next to it in E3 (both with the appropriate custom formats for the units); the converted value is in F3, using this formula:

=IF(ISBLANK(E3)+ISBLANK(D3)=0,"Clear D3 or E3!",IF(ISBLANK(E3),(IF(ISBLANK(D3),"Enter °C in D3 or °F in E3.",TEXT(D3*9/5+32,"###0.0""°F"""))),TEXT(5/9*(E3-32),"###0.0""°C""")))

May not be the most elegant solution and uses an extra cell, but it does what I want it to.


This Site

Got a version of Excel that uses the ribbon interface (Excel 2007 or later)? This site is for you! If you use an earlier version of Excel, visit our ExcelTips site focusing on the menu interface.

Newest Tips
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

(Your e-mail address is not shared with anyone, ever.)

View the most recent newsletter.