MS Excel: LET function assigns results names to calculation results

The LET function in Excel allows you to assign names to calculation results or expressions and reuse them within a formula. It enhances performance, readability, and maintainability by avoiding repetition of the same expression.

Syntax

=LET(name1, name_value1, [name2, name_value2, …], calculation)

Parameters:

Argument	Description
name1	The first variable name you want to define
name_value1	The value or expression to assign to name1
name2, etc.	(Optional) Additional name-value pairs
calculation	The final expression that uses the defined names

You can define up to 126 name-value pairs.

Simple Example

=LET(x, 10, y, 5, x + y)

Variable	Value
x	10
y	5

Result: 15

Real-World Example – Cleaner Formula

Suppose you calculate tax on a sales value in A1 with a tax rate of 18%.

Without LET:

=A1*0.18 + A1

With LET:

=LET(sale, A1, taxRate, 0.18, sale * taxRate + sale)

Component	Value
sale	A1 (e.g., 100)
taxRate	0.18

Easier to understand: adds tax to the sale total.

Performance Boost Example

If you’re repeating an expensive formula, such as SUM(A1:A1000) multiple times:

Without LET:

=SUM(A1:A1000)/COUNT(A1:A1000) + SUM(A1:A1000)*0.1

With LET:

=LET(total, SUM(A1:A1000), avg, total/COUNT(A1:A1000), avg + total*0.1)

Faster and more efficient, especially with large datasets.

Nesting LET with Other Functions

You can use LET inside larger formulas to make them modular.

Example with IF and LET:

=LET(score, A1, IF(score >= 60, "Pass", "Fail"))

Summary

Feature	Description
Function Name	LET
Purpose	Assign names (variables) inside a formula
Return Type	The result of the final expression
Use Case	Simplify formulas, improve performance
Availability	Excel 365 and Excel for Web

Notes

• Names must start with a letter and cannot be cell references.

• Variables are only available inside the formula—they are not global.

• If the same name is used multiple times, the last one overrides the earlier one.

Related Functions

Function	Description
LAMBDA	Define custom functions with parameters (Excel 365)
IF	Conditional logic
SUM	Total of a range
TEXT	Format numbers and values

Final Thoughts

The LET function is one of Excel’s most powerful new features, enabling cleaner, faster, and more maintainable formulas. It’s especially useful in advanced spreadsheets and when working with large datasets or repeated expressions.