LET Function

Excel 365 Math & Trig

The Excel LET function assigns names to values or calculations inside a formula, then uses those names in a final result — making long formulas readable and faster by computing each piece only once.

Quick answer:

=LET(x,5,x*2) names x = 5, returns x*2 = 10

Syntax

=LET(name1, value1, [name2, value2, ...], calculation)

Argument		Description
`name1`	Required	The name for the first value or calculation.
`value1`	Required	The value or expression assigned to name1.
`name2, value2, ...`	Optional	Additional name/value pairs. Later names can reference earlier ones.
`calculation`	Required	The final expression that uses the names and produces the result.

How to use it

LET takes pairs of name and value, finishing with a calculation that uses those names. It reads like defining variables before the math.

=LET(x, 5, x*2) // x = 5, result = 10

=LET(r, A1:A10, SUM(r)/COUNT(r)) // names a range once, returns its average

Beyond readability, LET is a performance win: a calculation named once is evaluated once, even if the name is used many times in the final expression. Compare a sprawling formula that repeats FILTER(...) three times to one that names it data and reuses it.

Names go in pairs. Every name must be immediately followed by its value, and the very last argument is always the calculation — never a name without a value.

Try it: interactive demo

Live demo

Pick a LET example to see the formula and its result.

example

Result:

Practice workbook

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Frequently asked questions

What problem does LET solve?

It removes repetition. Instead of writing the same sub-expression several times in one formula, you name it once and reuse the name — making the formula shorter, easier to read, and faster because each named calc runs only once.

How are the arguments ordered?

In name/value pairs, ending with the calculation: =LET(name1, value1, name2, value2, calculation). The final argument must be the result expression, not a dangling name.

Can one name use another name?

Yes. Later definitions can reference earlier ones, so you can build up a calculation step by step: =LET(a, 5, b, a*2, a+b) returns 15.

Which Excel versions support LET?

LET is available in Microsoft 365 and Excel for the web. It is not in Excel 2019 or earlier perpetual versions.

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Related functions: SEQUENCE · LAMBDA · SUM · FILTER · RANDARRAY