Introduction to the New LET Function in Microsoft 365 The bane of many Excel users is having to repeat portions of a calculation two or more times within a single formula. Any sort of repetition in Excel formulas can be fraught with risk, as edits in turn must be made multiple times. In the coming months Microsoft 365 subscribers will have access to the new LET function that allows you to assign a nickname to a calculation, you then instead of repeating the calculation two or more times you use the nickname instead. This means if you need to edit the calculation that is used more than once that you do so from a single place in the formula. Let’s try this out with a simple example shown in Figure 1.
If we want to mask a division by zero (#DIV/0!) error, the simplest way is to use the IFERROR function, as shown in cell C4. But let’s use an older method that predates IFERROR to set the stage for the LET function. As shown in cell C2 the ISERROR function can be used inside the IF function to determine if part of a calculation will return an error. This means we need to repeat A2/B2 twice in the formula. Cell C3 illustrates how we can use the LET function in this scenario. The LET function supports up to 126 name/namevalue pairs. In this case we have one name, “calc” and one name value, A3/B3. Since we don’t need any other name/namevalue pairs our next argument in the formula is our calculation, which is the IF/ISERROR combination. Anywhere that we would have listed A3/B3 we can now just use the word calc instead. This has significant potential to streamline writing complex formulas and improve their integrity as well.