Formulas and Variables in Flow
By the end of this lesson, you'll be able to:
- Write a formula resource for use in Flow logic
- Use variables to pass and store values through a Flow
Prerequisites: Before-Save vs. After-Save Flows
Formula resources
A Formula resource in Flow is defined once, using standard Salesforce formula syntax and referencing other Flow variables or record fields with merge field syntax ({!VariableName}), and can then be reused anywhere else in the Flow — decisions, assignments, screen text — without recalculating it in multiple places.
Variables
A Variable resource holds a single value of a declared data type (Text, Number, Boolean, Record, Collection) for use as the Flow runs — set via an Assignment element, read via merge field syntax anywhere downstream. Record and Collection variables specifically hold whole sObject records or lists of them, not just primitives.
A reusable Formula resource
Formula resource "Discounted_Total":
{!Var_Amount} - ({!Var_Amount} * {!Var_DiscountPercent} / 100)
Referenced later in a Screen element's display text:
Your total after discount is: {!Discounted_Total}The Formula resource is calculated once and can be referenced by name ({!Discounted_Total}) wherever it's needed downstream — exactly like a formula field, but scoped to this one Flow.
Exercise
Write a Flow formula resource that computes a Number variable Var_Price's value with 15% VAT added.
Show hint
Multiply Var_Price by 1.15, or add Var_Price * 0.15 to itself.
Formulas and Variables in Flow — Quick Check
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Summary
Flow's Formula resource type lets you compute a value using the same formula language used in formula fields and validation rules, referenced anywhere in the Flow via merge fields — variables, meanwhile, hold and pass values between elements as the Flow runs.