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How to Fix Incorrect Task Duration Calculations in Project for the Web

Maira Mehtab Sep 25, 2026 869 views

Question details

Users need to correct task durations and finish dates that are calculating improperly in their project plans.

How to Fix Incorrect Task Duration Calculations in Project for the Web

Product: Microsoft Project for the Web
Device & OS: not provided
Scenario: Managing task schedules, timelines, and automated date dependencies.
Observed behavior: Task durations and finish dates calculate incorrectly, often caused by unintended manual constraints indicated by a star beside the Finish date.

Before you start

Verify whether the calculation issue is happening across multiple project plans or if it is isolated to a single specific project plan.

Solution 1Recommended

Remove Unintended Task Constraints

Use this solution when you see a star icon next to a task date, which prevents the system from automatically calculating durations.

In Project for the web, manually entering a start or finish date automatically applies a date constraint to that task. This constraint overrides automated dependency scheduling and can lead to incorrect duration calculations.

Locate constrained tasks

Check your project timeline for any Finish dates that have a star icon next to them. This star indicates that a manual constraint is currently active.

Access the calendar settings

Click on the specific date or the calendar icon associated with the constrained task.

Remove the constraint

Select the 'Remove Constraint' option from the calendar menu. The date will reset, allowing the system to recalculate the duration automatically based on your set dependencies.

Automatic Scheduling Restored: Once constraints are removed, Project for the web will dynamically adjust start dates, finish dates, and durations based on your project's logical dependencies.

Solution 2

Escalate Isolated Plan Errors to Microsoft Support

Use this solution if removing constraints and clearing dependencies does not fix the calculation issue, especially if it only affects one specific project plan.

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While WPS Office does not directly replace Microsoft Project, it provides a comprehensive, lightweight, and free office suite. You can easily manage project timelines, create Gantt charts, and track task durations using WPS Spreadsheet, while maintaining perfect compatibility with Microsoft Office formats.

1. Download and Install: Download WPS Office from the official website and follow the simple installation instructions.
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Frequently Asked Questions

Why is there a star next to my task's Finish date?

A star beside the Finish date indicates that a manual constraint has been set on the task. This usually happens when you manually enter a start or finish date instead of letting the project dependencies calculate it automatically.

Can manual date entries affect automatic scheduling?

Yes. Manually entering dates overrides the automatic scheduling engine. The system locks that date as a constraint, which can cause unexpected task durations or prevent subsequent tasks from shifting correctly when earlier tasks are delayed.

What should I do if clearing constraints doesn't fix the task duration?

If you have removed all constraints and dependencies but the task duration still calculates incorrectly in a single project plan, the plan might be corrupted. You will need to contact Microsoft Support through the Microsoft 365 admin center for further assistance.

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