How to find the critical path in an .mpp file

The critical path is the chain of tasks that decides when the project finishes. Here is how to see it in a Microsoft Project file on a Mac or iPad.

Updated 17 October 2026

Quick answer

Open the .mpp in MPP Studio: the critical path is drawn in red on the Gantt chart. Press ⇧⌘C to turn it off or on. Any delay to a red task delays the finish date.

Lengthen a long-lead task to 60 days and the red critical path re-routes through it.

What the critical path is

Tasks are linked: one can’t start until another finishes. Follow the links from the start to the finish and the longest chain is the critical path. Any delay to a task on it delays the whole project. Tasks off the path have slack (float): they can slip a little without moving the end date.

A worked example

In the Riverside Clinic fit-out below, the red chain runs from the site survey through permits, strip-out and first fix to fit-out and handover. The long-lead imaging equipment is not red: it has slack, so a delay of a few days there doesn’t move handover. Lengthen it enough, as in the video above, and it becomes critical.

MPP Studio on iPad: the schedule with phases in the sidebar, the task grid and a Gantt chart with the critical path in red
The Riverside Clinic programme on iPad. Red bars and links are the critical path; the status bar counts critical tasks.

See it in MPP Studio

  1. Open the .mpp file.
  2. The critical path is drawn in red on the Gantt chart by default.
  3. Press ⇧⌘C to turn the highlight off or on.

The path is calculated from the file’s own links, lags, constraints and calendars.

Use it

  • Focus on red tasks. When the forecast finish slips, the cause is on the critical path.
  • Check after every change. Shortening a critical task can move the critical path elsewhere.
  • Track against the baseline. With the plan locked as a baseline, you can see how far critical tasks have slipped.

Questions people ask

How do I show the critical path without Microsoft Project?

Open the .mpp in MPP Studio on Mac or iPad; the critical path is shown in red by default.

What is slack or float?

How long a task can slip without delaying the project finish. Critical tasks have none.

See what drives your finish date

Open any .mpp on Mac or iPad and see the critical path in red.

Coming soon: get notified

Related

Microsoft and Microsoft Project are trademarks of Microsoft Corporation. MPP Studio is not affiliated with Microsoft. Other product names are trademarks of their owners. Competitor details are taken from their own websites and App Store listings in October 2026; check with the vendor for current prices.