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Excel’s LET function gives a name to a value or calculation inside a formula, so you can refer to it by name later in that same formula. For example, =LET(x,5,SUM(x,1)) returns 6. Use LET to make a complex formula easier to read and to avoid writing the same expression repeatedly.
What does Excel’s LET function do?
Microsoft Support describes LET as a function that assigns names to calculation results. Those names exist only within the LET formula where they are declared; they do not become workbook-wide names or reusable functions. Microsoft’s LET function reference explains the syntax and supported editions.
Think of LET as a way to label the steps of a formula. Instead of repeating a calculation or deciphering a long string of cell references, you can give an intermediate result a meaningful name and use that name in the final calculation.
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The syntax is =LET(name1, name_value1, calculation_or_name2, [name_value2, calculation_or_name3...]). Enter one or more name-and-value pairs, then finish with a calculation that returns the result. The square brackets in Microsoft’s syntax indicate optional arguments; do not type them as part of the formula.
- Start with
=LET(. - Enter a name, followed by the value or calculation to assign to it.
- Add further name-and-value pairs as needed, separating arguments with commas.
- Finish with the calculation that uses those names, then close the parenthesis.
For example, =LET(x,5,SUM(x,1)) assigns 5 to x and then adds 1, returning 6. A LET formula needs at least one name/value pair and a final calculation. It can contain as many as 126 name/value pairs.
Choose valid, useful names
Names must follow Excel’s defined-name rules. Microsoft notes that a name must start with a letter and cannot be confused with range syntax. For example, c is invalid because it conflicts with R1C1-style references. Descriptive names such as taxRate, filteredRange, or netSales make a formula’s intent easier to follow than cryptic letters.
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How can LET make a formula easier to read?
Consider a formula that filters a sales table for a particular person and replaces blank results with a dash. Naming the criterion and filtered results makes those stages visible:
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=LET(filterCriteria,"Fred",filteredRange,FILTER(A2:D8,A2:A8=filterCriteria),IF(ISBLANK(filteredRange),"-",filteredRange))
Here, filterCriteria identifies who to select, filteredRange holds the filtered data, and the final IF handles blanks. If the criterion changes, you can edit its assigned value without hunting for every occurrence of the name in the rest of the formula.
LET can also reduce repeated work when a formula uses the same expression more than once. Microsoft says LET allows a named expression to be calculated once and then referenced by name. In its specific sales-filter example, Microsoft reported that the LET version ran “twice as fast” as the original. That is an example-specific result, not a general speed guarantee for every workbook. Microsoft’s 2020 Excel Blog announcement describes the motivation behind the function.
Does LET work in Excel for the web?
Microsoft lists LET for Excel for Microsoft 365, Excel 2024, and Excel 2021, including the Windows and Mac editions covered by its function reference. Microsoft’s function-category page says LET is not available in Excel for the web. Check Microsoft’s current function list for the latest availability information.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteWhen should I use LET instead of LAMBDA or a workbook name?
Use LET when you want to name intermediate values or calculations in one formula. The names are local to that formula, so they are not available elsewhere in the workbook.
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Use LAMBDA when you want to create a reusable custom function that can be called by a friendly name. Microsoft’s LAMBDA function reference explains how to test a LAMBDA and then place it in Name Manager. A workbook-defined name serves a different purpose: it names a value or range for use beyond a single LET expression.
Quick Recap
| Option | Scope | Best fit |
|---|---|---|
| LET | One formula | Naming intermediate values and calculations inline |
| LAMBDA | A reusable named function | Creating a custom function callable from other formulas |
| Workbook-defined name | Workbook-level | Naming a value or range for use across formulas |
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