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Why Do Microsoft Project Task Work Hours Not Match?

John Wilson Sep 27, 2026 869 views

Question details

The user needs to understand why two Microsoft Project tasks with identical durations calculate different total work hours.

Why Do Microsoft Project Task Work Hours Not Match?

Product: Microsoft Project
Device & OS: not provided
Scenario: Planning or reviewing a project schedule where task durations match but the calculated total work amounts differ unexpectedly.
Observed behavior: Work hour totals diverge between tasks that have the exact same duration, causing confusion in resource or project planning.

Before you start

Verify that your project baseline is not unexpectedly skewing your view, and note down the start and finish dates of the affected tasks before making structural changes.

Solution 1Recommended

Verify Project, Task, and Resource Calendars

Different working hours set across various calendars will cause identical duration tasks to calculate different work totals.

Microsoft Project calculates work based on the specific calendar applied. If one task uses a standard 8-hour day calendar and another is assigned a resource with a 6-hour day calendar, the resulting work hours will differ even if both tasks last for 5 days.

Check the Project Calendar

Navigate to the 'Project' tab, click 'Project Information', and check which Base Calendar is applied to the overall project.

Verify Task-Specific Calendars

Double-click the specific task to open 'Task Information', go to the 'Advanced' tab, and check if a specific calendar is selected in the 'Calendar' drop-down menu.

Confirm Resource Working Times

Go to the 'View' tab, select 'Resource Sheet', and double-click the assigned resource. Check their specific 'Working Time' settings to ensure they match the expected daily hours.

Verify Project, Task, and Resource Calendars

Calendar Priority: Resource calendars generally override the project calendar. If a task calendar is set to 'Scheduling ignores resource calendars', the task calendar takes precedence.

Solution 2

Check Task Types and Assignment Units

Task types and assignment units dictate the formula Project uses (Work = Duration × Units) to calculate your project scheduling.

Solution 3

Confirm Auto vs. Manual Scheduling

Manually scheduled tasks do not automatically recalculate work or duration when changes occur.

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Frequently Asked Questions

How does the 'Effort Driven' setting impact task work?

If a task is Effort Driven, the total work remains constant. When you add new resources to the task, Microsoft Project decreases the duration rather than increasing the total work hours.

Can start and finish dates cause work hour mismatches?

Yes. If a task's duration crosses over weekends, holidays, or non-working days defined in the calendar, the actual working time available changes, which directly affects the total calculated work hours.

Why did my work hours change when I changed a resource?

Work hours recalculate based on the new resource's specific base calendar and their default assignment units. If the new resource works fewer hours per day, the total work for the same task duration will decrease.

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