Let() for named variables in FileMaker calculations

Intermediate

Let() allows you to declare named variables within a calculation, avoiding repeated sub-expressions and making complex formulas readable. Learn the syntax, scope, and best practices.

What you'll learn

The syntax for declaring one or more variables in Let()
How Let() improves readability and avoids repeated sub-expressions
The scope of Let() variables — they exist only within the Let expression

Let ( [ var = expression ; ... ] ; result ) assigns named variables for use within a calculation, making complex formulas readable and efficient by evaluating sub-expressions once.

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Declare a variable in Let() for a cleaner calculation

Without Let(), the same sub-expression must be repeated. With Let(), compute it once and reference the name.

FileMaker Script

// Without Let — confusing and slow (discount computed twice)
If ( price * quantity * discountRate > 100 ;
  price * quantity - price * quantity * discountRate ;
  price * quantity
)

// With Let — clean and computed once
Let ( [
  subtotal     = price * quantity ;
  discountAmt  = subtotal * discountRate
] ;
  If ( discountAmt > 100 ; subtotal - discountAmt ; subtotal )
)

Aggregate functions in FileMaker: Sum, Count, Average, Max, Min While() for iterative loops in FileMaker calculations (FM 19+)