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How to Configure Microsoft Project to Calculate Durations in Hours

Olivia Miller Oct 15, 2026 868 views

Question details

The user needs to configure Microsoft Project to calculate and display task and summary durations in hours instead of days for a continuous, around-the-clock project.

How to Configure Microsoft Project to Calculate Durations in Hours

Product: Microsoft Project
Device & OS: not provided
Scenario: Managing a 24-hour project that requires precise hourly tracking, continuous work scheduling, and an hourly timescale display.
Observed behavior: By default, Microsoft Project calculates durations in days based on a standard working calendar, which needs to be adjusted to a 24-hour calendar and hourly duration entry mode.

Before you start

Ensure you have administrative or editing access to your Microsoft Project file, and consider backing up your project timeline before making significant changes to the base working calendar.

Solution 1Recommended

Configure Duration Settings and Apply a 24-Hour Calendar

Change the default schedule options to hours, apply a 24-hour calendar for continuous work, and adjust your timescale view.

To properly track an around-the-clock project, you must align the duration entry settings, the project's working time calendar, and the visual timescale to function in continuous hours rather than standard work days.

Set Default Duration to Hours

Navigate to File > Options > Schedule. Locate the scheduling options and set 'Duration is entered in' to 'Hours'.

Change Working Time to 24 Hours

Go to Project > Project Information > Change Working Time. From the calendar dropdown list, select the '24 Hours' calendar to allow continuous scheduling without off-hours.

Adjust Timescale Increments

Click View > Timescale. In the timescale settings, set the Major units to 'Hours'. You can optionally set the Minor units to 15 or 30 minutes for more granular tracking.

Enter Task Durations

In your task list, type the duration directly in hours by appending an 'h' to the number (e.g., '4h' or '12h'). Summary tasks will automatically calculate their durations based on these subtasks.

Configure Duration Settings and Apply a 24-Hour Calendar

Automatic Calculation: Once configured, you do not need to manually adjust summary task durations; they will seamlessly calculate the total hours based on the subtasks assigned beneath them.

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Frequently Asked Questions

Why are my summary tasks showing 0 hours in Microsoft Project?

Summary tasks calculate their duration automatically from their nested subtasks. If the subtasks have no duration set or are marked as milestones, the summary task will reflect zero. Do not manually overwrite summary task durations.

Can I use 15-minute increments in my Microsoft Project timescale?

Yes, you can adjust this granularity by navigating to View > Timescale, setting your Major units to Hours, and your Minor units to 15 Minutes.

How do I ensure subtasks don't pause during non-working hours?

You must change the project calendar to continuous work. Go to Project > Project Information > Change Working Time and select the '24 Hours' calendar. This ensures durations calculate around the clock without stopping for standard evenings or weekends.

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