Forms Logic & Calculations

Forms Logic allows you to build dynamic, intelligent forms that respond in real time to user input. Using a When / Then framework, you can show or hide fields, enforce requirements, auto-fill values, and even prevent submission — all without custom code.

This enables forms to adapt to real-world business rules, reduce user error, and streamline data collection.

How Forms Logic Works

To access the Form Logic feature, you can select the logic tab from the Form builder. 

Forms Logic is built using rules, each made up of two parts:

• When — conditions that must be met

• Then — actions that occur when those conditions are true

Multiple rules can exist on the same form and are evaluated as users interact with the form.

Building Conditions (When)

Each condition contains three components:

1. Field - Select the form field you want to evaluate.

2. Operator - Determines how the field is evaluated. Available operators depend on the field’s data type.

3. Value - The value to compare against. This may be a static value, another field, or a calculated value.

Grouping Conditions

You can combine conditions to create more complex logic:

• All conditions are true (AND)
  Every condition in the group must be met.

• Any condition is true (OR)
  At least one condition in the group must be met.

Supported structure:

• Multiple conditions per group

• Multiple condition groups

• One level of nesting, for example:
  (Condition A OR Condition B) AND (Condition C OR Condition D)

Notes

• Selecting Add condition adds another condition to the current group.

• Selecting AND or OR under a group creates a new condition group.

• Rule and group names are for organization only and do not affect behavior.

Available Operators by Field Type

Operators vary based on the field selected.

Text / String Fields

(Short Text, Long Text, Name sub-fields, Email, Phone, Address sub-fields)

• Is / Is not

• Is empty / Is not empty

• Contains / Does not contain

• Starts with / Does not start with

• Ends with / Does not end with

• Length comparisons (longer than, shorter than, equal to, etc.)

Number Fields

(Number)

• Is / Is not

• Is empty / Is not empty

• Greater than / Less than

• Greater than or equal to / Less than or equal to

Date Fields

(Date, Time, Date/Time)

• Is / Is not

• Is before / Is after

• Is empty / Is not empty

Option Fields

Single-option fields (Radio, Dropdown):

• Is / Is not

• Is empty / Is not empty

Multi-option fields (Checkbox):

• Is / Is not

• Contains / Does not contain

• Is empty / Is not empty

Value Input Options

Depending on the field type and operator, values can be provided in several ways:

• Static values — Manually entered values

• Field references — Values from other fields in the same form

• Formulas — Basic numeric calculations

• Date picker — For date-based comparisons

• Calculator — Available for numeric value entry

Important

• Option-type fields (Radio, Checkbox, Dropdown) do not allow manual values.
  Values must come from existing options or mapped data.

Actions (Then)

When conditions are met, you can trigger one or more actions:

• Hide, exclude data — Visually hides the field from the user, removes required validation and excludes data for that field from the submission
• Show, include data —  Visually show the field from the user, require  required validation and include the data for that field from the submission (opposite action of “Hide, exclude data”) 
• Make required — Makes a field mandatory for form submission
• Make optional — Removes the requirement, making the field optional
• Make read-only —  Prevents users from editing the field
• Make editable — Allows users to modify a field that was set to read-only
• Make invisible - Only visually hides a field on the form
• Make visible - Only visually hides a field on the form
• Fill, read-only - Populates a field with a value or calculation and sets it to be uneditable by the end user
• Disable submission — Block form submission

Fill and Read-Only Behavior

• Fields are filled and locked only while the When condition is true.

• If the condition becomes false:

  • The field is no longer filled

  • The field becomes editable unless it was already set to read-only

Filling values

• Number fields support calculations

• Other field types can be filled using:

  • Values from other fields (current or previous forms)

  • Static values

Data Mapping in Logic

Forms Logic supports data mapping from:

• Fields in the current form

• Fields from earlier steps in the workflow

This allows you to:

• Use previously collected data in logic

• Avoid adding extra fields solely for logic purposes

Data type rules apply

• The referenced field’s data type must be compatible with the target field.

Logic and Calculations: Understanding "Then" Actions

When you set up Logic and Calculations in Forms, the "Then" section provides several actions you can apply to fields. Understanding these options is important because some control field settings while others affect the data itself.

Opposite Pairs: Field Settings

These options work as opposites, toggling field settings on and off:

Make visible ↔ Make invisible

• Make visible: Only visually shows a field on the form
• Make invisible: Only visually hides a field on the form

Make required ↔ Make optional

• Make required: Makes a field mandatory for form submission
• Make optional: Removes the requirement, making the field optional

Make editable ↔ Make read-only

• Make editable: Allows users to modify a field that was set to read-only
• Make read-only: Prevents users from editing the field (they can see it but not change it)

Data-Affecting Actions

These options control both visibility AND what happens to the data:

Show, include data

• Displays the field to the user
• Includes the field's data in form submissions and calculations

Hide, exclude data

• Visually hides the field from the user
• Removes validation requirements (requirements) 
• Excludes the field's data from submissions and calculations
• Note: This is different from "Make invisible," which only affects visibility

Fill, read-only

• Populates a field with a value or calculation
• Makes the field read-only so users cannot edit it

Disable submission

• Prevents the form from being submitted when the logic condition is met

Important Note for Formstack Forms Users

If you migrated from Formstack Forms, you may have been familiar with "Hide" meaning "visually hide, remove validation, and exclude data" and "Show" meaning the opposite. The new system maintains this behavior:

• Hide, exclude data = your previous "Hide" behavior
• Show, include data = your previous "Show" behavior

The "Make invisible/Make visible" options are simpler, they only control whether the field appears on screen without affecting data handling.

Limitations

• File fields cannot be used in logic conditions

• Only one level of condition nesting is supported

• Date, Time, and Date/Time fields can only be compared to static values

  • At this time, these fields cannot be compared to other fields using logic

Troubleshooting Common Issues

Hidden elements overriding visible ones

Logic follows the form hierarchy:

Pages → Sections → Fields

If a parent element is hidden, all child elements remain hidden — even if a rule explicitly shows a child field.

Example

• Page is set to Hide

• Field on that page is set to Show

The field remains hidden because the page (parent) is hidden.