📑 What You’ll Learn in This Guide

• What is the Excel LET Function?
• LET Function Syntax Explained
• Basic LET Function Example
• Advanced: Using LAMBDA Inside LET to Create Custom Functions
• Step-by-Step Formula Breakdown
• 5 Key Benefits of Using LET
• Practical Use Cases
• Frequently Asked Questions

What is the Excel LET Function?

The Excel LET function is a powerful formula that allows you to declare variables inside your Excel formulas — just like you would in any programming language. Introduced in Excel 2021 and Microsoft 365, the LET function transforms how you write complex formulas.

Think of it this way: before LET, writing formulas in Excel was like solving a math problem where you had to repeat the same calculation over and over. Now, you can define a calculation once, give it a name, and reuse it as many times as you need.

Availability: Excel 2021, Excel 2024, Microsoft 365 (Windows & Mac), Excel for the web

Excel LET Function Syntax

The syntax of the LET function is straightforward:

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

Parameters Explained:

Basic LET Function Example

Let’s start with a simple example. Suppose you want to calculate the total price including tax:

Without LET (Repetitive):

=IF(B2*1.18>1000, B2*1.18*0.95, B2*1.18)

Notice how B2*1.18 is calculated THREE times!

With LET (Clean & Efficient):

=LET(
    PriceWithTax, B2*1.18,
    IF(PriceWithTax>1000, PriceWithTax*0.95, PriceWithTax)
)

Now PriceWithTax is calculated ONCE and reused. This makes your formula:

• ✅ Easier to read
• ✅ Faster to calculate
• ✅ Easier to maintain

🚀 Advanced: Using LAMBDA Inside LET to Create Custom Functions

Here’s where the Excel LET function becomes truly powerful. Most tutorials only show you how to store values. But the real magic? You can store entire functions as variables using LAMBDA!

This means you can create a custom function inside your formula — define it once, and call it with different parameters. No VBA required!

The Formula That Changes Everything:

=LET(
    MyVal, F2,
    
    MySwitch, LAMBDA(val,
        SWITCH(val,
            "a", B3#,
            "b", SUM(B3#),
            "c", 300,
            0
        )
    ),
    
    MySwitch(MyVal)
)

🎯 How It Works in Practice

Here’s what happens when users change the value in cell F2:

5 Key Benefits of Using the Excel LET Function

1. Improved Readability

Named variables make complex formulas self-documenting. Anyone can understand what TaxAmount means versus B2*0.18.

2. Better Performance

When you use LET, Excel calculates each variable only once, even if you reference it multiple times. This significantly speeds up large workbooks.

3. Easier Maintenance

Need to change a calculation? Update it in one place. No more hunting through a formula to change the same expression in 5 different spots.

4. Reduced Errors

Defining expressions once eliminates copy-paste errors and inconsistencies that creep in when repeating the same logic.

5. Custom Functions Without VBA

By combining LET with LAMBDA, you can create custom functions that work like native Excel functions — no programming knowledge required!

🛠️ Practical Use Cases for LET + LAMBDA

1. Dynamic Report Switching

Let users choose between different aggregations (sum, average, count, max) with a single cell input — exactly like our example above.

2. Unit Conversions

Create a custom conversion function that switches between kilometers/miles, Celsius/Fahrenheit, or any units based on user selection.

3. Financial Scenario Analysis

Switch between “best case,” “worst case,” and “base case” scenarios dynamically without changing the underlying formula.

4. Data Validation Messages

Return different validation messages based on input conditions — all from a single smart formula.

5. Conditional Formatting Logic

Build complex formatting rules as reusable functions that can be applied across multiple scenarios.

LET vs Traditional Formulas: A Comparison

❌ Traditional Nested IF (Hard to Read):

=IF(F2="a",B3#,IF(F2="b",SUM(B3#),IF(F2="c",300,0)))

✅ With LET + LAMBDA (Clean & Modular):

=LET(MyVal,F2,MySwitch,LAMBDA(val,SWITCH(val,"a",B3#,"b",SUM(B3#),"c",300,0)),MySwitch(MyVal))

The LET version may look longer, but it’s:

• ✅ More readable (each component is named)
• ✅ More scalable (easy to add more options)
• ✅ More reusable (the LAMBDA can be called multiple times)

❓ Frequently Asked Questions About Excel LET Function

Q: Which Excel versions support the LET function?

A: The LET function is available in Excel 2021, Excel 2024, Microsoft 365 (Windows and Mac), and Excel for the web. It’s also available in Google Sheets.

Q: Can I use LET to create permanent named functions?

A: Variables created with LET only exist within that specific formula. For permanent named functions, combine LET with LAMBDA and save it in the Name Manager.

Q: How many variables can I create in a single LET function?

A: Excel allows up to 126 name-value pairs in a single LET function.

Q: Does LET improve formula performance?

A: Yes! When you reference a variable multiple times, Excel calculates it only once. This can significantly speed up complex formulas.

Q: Can I nest LET functions?

A: Absolutely! You can nest LET functions, and the inner LET can access variables from the outer LET.

Q: What’s the difference between LET and Named Ranges?

A: Named Ranges are defined in the Name Manager and work across the entire workbook. LET variables exist only within the formula where they’re defined — making them safer and more portable.

🎯 Key Takeaways

1. LET is your in-cell editor — Declare variables, structure logic, write cleaner formulas
2. Variables can store functions — Using LAMBDA inside LET creates reusable custom functions
3. Performance matters — LET calculates each variable once, even if used multiple times
4. Readability is key — Named variables make complex formulas self-documenting
5. No VBA required — Create powerful custom functions with just formulas