How to Use the LET Function in Excel

LET lets you name a value once and reuse it inside the same formula. The result is shorter, faster, and far easier to read — especially when you keep repeating the same lookup or calculation. Here is how it works.

By the Quiriz Team · Published July 28, 2026 · 4 min read

The quick answer: =LET(name, value, calculation). You name a value once, then use that name in the final calculation. Add as many name/value pairs as you like before the calculation — it makes long formulas shorter, faster, and readable.

The syntax

LET is a list of name/value pairs followed by one final calculation:

=LET(name1, value1, name2, value2, calculation)

Each name must start with a letter. The very last argument is always the calculation that produces the cell's result, and it can use every name you defined before it.

A simple example

=LET(tax, 0.08, price*(1+tax)) names the tax rate tax, sets it to 8%, and then applies it. Change the rate in one place and the whole formula follows. It reads like a short instruction instead of a wall of numbers.

Before and after: a repeated lookup

Here's a formula that looks up an amount and repeats the lookup three times — once to test it, once to display it, once as a fallback:

=IF(XLOOKUP(id,ids,amts)>0, XLOOKUP(id,ids,amts), "none")

With LET, you compute the lookup once, name it, and reuse the name:

=LET(found, XLOOKUP(id,ids,amts), IF(found>0, found, "none"))

Shorter to read, and Excel does the lookup a single time instead of twice.

When to reach for LET

Use it when a formula repeats the same sub-calculation, or when it has grown long enough that you can no longer tell at a glance what it does. Naming the moving parts turns an opaque one-liner into something you — or the next person — can actually read.

LET needs Microsoft 365 or Excel 2021 and later. On older versions it isn't available, and you'll get a #NAME? error. Google Sheets has its own LET with the same idea.

Or skip the formula entirely

LET is worth learning, but sometimes you just want the answer, not another formula to maintain. With the Quiriz add-in you can type =QUIRIZ.ASK("total amount for open deals") in a cell and get the answer back in plain English — no nesting, no naming, no lookup to debug. It's a different way to get at the same result.

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Frequently asked questions

What does the LET function do in Excel?

LET assigns names to calculation results inside a formula, then uses those names in a final calculation. It makes formulas shorter and easier to read, and it can make them faster because a value wrapped in a name is computed once instead of every time it appears.

What is the syntax of LET?

LET takes one or more name/value pairs followed by a final calculation: =LET(name1, value1, name2, value2, ..., calculation). Each name must start with a letter, and the final argument is always the calculation that produces the result.

Does LET make formulas faster?

It can. If your formula repeats the same expensive calculation — for example the same XLOOKUP three times — wrapping it in a LET name computes it once and reuses the result, which reduces the work Excel does. For trivial formulas the speed difference is negligible; the readability gain is the main benefit.

Which versions of Excel have LET?

LET is available in Microsoft 365 and Excel 2021 and later. It is not in Excel 2019 or earlier perpetual versions. Google Sheets also has a LET function with the same idea.