Calculator Field
This module allows site builders to create fields that automatically calculate their value based on a mathematical formula using other fields. It provides live, client-side calculations on edit forms and server-side calculations for displaying the results.
Introduction
Calculator Field lets site builders compute values from other fields using a simple tokenized math formula (e.g., “[field_price] * [field_quantity]”), with live updates on edit forms and computed output on view.
Features
Build formulas with field tokens: “[field_a] + ([field_b] * 0.2)”
Live calculation on node edit forms (no save required)
Formatter computes at view time (server-side) for accurate output
Optional display of:
Original formula
Formula with current field values substituted (e.g., “10.50 * 3”)
List of fields used and their values
Token picker for eligible fields (integer, float, decimal), excludes system fields
Post-Installation
Structure → Content types → Manage fields → Add “Calculator Field”
Structure → Content types → Manage form display → Edit “Calculator Widget”
Enter formula using tokens (click tokens to insert)
Structure → Content types → Manage display → Choose “Calculator Formatter”
Optional: enable “Show formula” and “Show formula with values”
Optional: add custom CSS classes
Clear caches if needed (drush cr)
Additional Requirements
Drupal core 10 or 11
Token module
Composer: composer require drupal/token
Recommended modules/libraries
None required. If you need stricter evaluation, consider a PHP math parser library to replace eval-based evaluation.
Similar projects
Computed/Calculated field modules. Calculator Field focuses on:
Simple, token-based formulas
Live JS updates on edit forms
On-the-fly, server-side computation via the formatter
Clean UI with token picker and optional formula displays
Supporting this Module
Contributions, issues, and feature requests are welcome on the project issue queue.
Community Documentation
Add tutorials, walkthroughs, or demo links here.