Most people write messy formulas that recalculate the same thing 3 or 4 times.
=LET() lets you name parts of your formula, store them once, and use them again and again — all in a single formula.
It makes your sheets faster, cleaner, and way easier to debug.

30-Second Walk-Through

Here’s what most people do:

excel
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=IF ( (A1+B1)*C1>100, (A1+B1)*C1, 0)

See the repetition?
Here’s the =LET() version:

excel
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=LET (total, (A1+B1)*C1, IF(total>100, total, 0))

Now if you ever need to adjust the logic, you do it in one place, not two or three.

Use-case: calculations that repeat inside your formula, like (price+tax)*qty
Bonus: LET can even be nested with LAMBDA for custom reusable functions.

Another way to explain it:

LET allows you to store calculations, makes your formula more efficient if you have to do something more than once.
For example,

=IF(VLOOKUP(A1,A2:B4,2)=0, 0, VLOOKUP(A1,A2:B4,2))

Here you did VLOOKUP twice but with LET, you can store it in a variable name of your choosing, say v.

=IF(VLOOKUP(A1,A2:B4,2)=0,0, VLOOKUP(A1,A2:B4,2))

Thanks for reading!