Currently, Jira does not provide a native admin or project setting to directly change how the Epic completion progress is calculated on the issue screen. The default progress bar is hardcoded and typically uses either issue count or story points, depending on board configuration and estimation settings.

It would be good to get the possibility to use the customised weighted formula for the progress bar to review the completion of tasks.

Workaround:

As a workaround, you can create your own custom progress calculation and display it on the Epic issue screen using a custom field and Jira Automation:

• Create a custom field (e.g., "Epic Completion").
• Set up an automation rule that:
  • Triggers on issue transitions (e.g., when a child issue is marked Done).
  • Looks up all child issues of the Epic.
  • Calculates progress using your preferred logic (issue count, story points, or a weighted formula).
  • Updates the custom field on the Epic.
• Display this custom field on the Epic issue screen and in dashboard gadgets.

Reference docs:

• Display Epic completion percentage on Jira Dashboard
• Calculate parent progress from child work item status in Jira Cloud