Understanding the LET Function

Written by Allen Wyatt (last updated August 12, 2023)
This tip applies to Excel Excel in Microsoft 365 and 2021

The LET function provides a very powerful way for you to create variables that you can use within a formula. This may sound strange, but it is quite easy to do. Consider the following very simple example:


There are three parts in this example. The first two parts define two variables named c and m and assigns values to those variables. So, in this example c is assigned the value 7 and m is assigned the value 8. The third part of the example is a formula that uses the variables, multiplying c times m. This is the value returned by the formula—56.

You can also, though, use variables within the definition of other variables. That is shown through this very small change to the previous example:


In this case, c is still assigned the value of 7, but m is assigned the value of c plus 2, which works out to be 9. Finally, the multiplication produces a result of 63. Usage of variables within definitions of other variables must be done in order, meaning that you can only use variables that were previously defined within the LET function. As an example, the following will not work because when a value is being applied to the c variable, the m variable has yet to be defined:


Remember that these are very simple examples, provided just so you can see how you can create variables, assign variables to them, and then use them in an equation. The important thing is that variables and values must be defined as pairs. You must define at least one such pair in the LET function, and you cannot define more than 126 such pairs. (That would make a very long formula, as well.)

For me, the real power of the LET function comes into play if you have formulas that repeat things over and over again. As an example, consider the following formula, which determines the first Friday within a range of dates specified in cells A2 and A3. (The formula is discussed more fully in this ExcelTip.)


If you rewrite this formula to utilize the LET function, then you can make it shorter:


All it does is to assign to the variable w the result of applying the WEEKDAY function to the date value in cell A2. This variable (w) is then used in the formula, resulting in a much shorter formula.

Here's another example of a formula that can be used to check the last two characters in a cell and, if they are equivalent to compass directions (NE, SE, NW, or SW), then make sure those are shown as uppercase. (This formula is discussed more fully in this tip.)

=IF(LOWER(RIGHT(A1,3))=" ne", LEFT(A1,LEN(A1)-2) & "NE",
IF(LOWER(RIGHT(A1,3))=" se", LEFT(A1,LEN(A1)-2) & "SE",
IF(LOWER(RIGHT(A1,3))=" nw", LEFT(A1,LEN(A1)-2) & "NW",
IF(LOWER(RIGHT(A1,3))=" sw", LEFT(A1,LEN(A1)-2) & "SW", A1))))

Here's how you could use the LET function to shorten the formula:

IF(sDir=" ne", sPart & "NE", IF(sDir=" se", sPart & "SE",
IF(sDir=" nw", sPart & "NW", IF(sDir=" sw", sPart & "SW", A1)))))

In this case two variables are defined (sDir and sPart) and another important thing is demonstrated—the LET function will work just fine with assigning text values to the variables.

The bottom line is that LET can be used to refashion very long formulas into much shorter formulas and make them easier to understand and maintain.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (9810) applies to Microsoft Excel Excel in Microsoft 365 and 2021.

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. ...


Creating Categories for Your Table of Authorities

A table of authorities is normally divided into separate sections based on categories you define. Here's how to create ...

Discover More

Too-Big Toolbars

Work around Words inability to have a multi-row toolbar.

Discover More

Footnotes for Tables

Word includes a powerful feature that allows you to add footnotes and endnotes to your document. What if you want them at ...

Discover More

Professional Development Guidance! Four world-class developers offer start-to-finish guidance for building powerful, robust, and secure applications with Excel. The authors show how to consistently make the right design decisions and make the most of Excel's powerful features. Check out Professional Excel Development today!

More ExcelTips (ribbon)

Using a Cell Value as a Worksheet Name in a Formula

Excel allows you to easily develop formulas that pull values from worksheets and workbooks other than the one in which ...

Discover More

Using the FORECAST Function

Excel provides a handy worksheet function that allows you to forecast values based upon a set of known values. This ...

Discover More

Colors in an IF Function

You can use the IF worksheet function to test for a number of different conditions or values. You can't use it to check ...

Discover More

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

View most recent newsletter.


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 9 + 4?

There are currently no comments for this tip. (Be the first to leave your comment—just use the simple form above!)

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

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.