name1 - First name to assign. Must begin with a letter.
value1 - The value or calculation to assign to name 1.
name2/value2 - [optional] Second name and value. Entered as a pair of arguments.
calculation - Calculation using assigned names and values.
The LET function is meant to make it easier to write more complex formulas, by making it possible to declare and assign values to variables inside a formula. Once a variable is named it can be assigned a static value, or a value based on a calculation. This allows a formula to refer to a variable by name as many times as needed, while the value of the variable is assigned in one place only.
Variables are named and assigned values in pairs (name1/value1, name2/value2, etc). LET can handle up to 126 name/value pairs, But only the first name/value pair is required. The calculation used to return a final result from LET always appears as the last argument to the function.
Below is the general form of the LET function with one variable:
After x and y have been declared and assigned values, the calculation provided in the 5th argument returns 15.
Typically, variables are not assigned static values but rather values that are calculated. For example, in the screenshot above, the formula uses the SEQUENCE function to generate all dates between May 1, 2020 and May 15, 2020: