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Why Microsoft Project Calculates Seven Days as Three Calendar Days

Chanuka Geekiyanage Oct 1, 2026 869 views

Question details

The user needs to understand why a 7-day task in Microsoft Project finishes in roughly 3 calendar days and how to fix this duration calculation discrepancy.

Why Microsoft Project Calculates Seven Days as Three Calendar Days

Product: Microsoft Project
Device & OS: not provided
Scenario: Entering a 7-day task duration into a project schedule.
Observed behavior: A task assigned a 7-day duration finishes after approximately 3 calendar days instead of spanning a full 7 calendar days.

Before you start

Check your current project calendar settings to see if you are using a 24-hour calendar or standard calendar, and note your default working hours per day.

Solution 1Recommended

Use Elapsed Days for the Task Duration

Use 'elapsed days' to force the task to calculate strictly by 24-hour calendar days, regardless of default working hour definitions.

In Microsoft Project, entering 'd' calculates time based on the default working hours (usually 8 hours = 1 day). If your project uses a 24-hour calendar, 7 days (56 hours) will finish in roughly 2.33 calendar days. Using elapsed days bypasses this.

Select the Duration field

Click directly on the Duration cell for the task that needs adjusting.

Enter the elapsed duration

Type '7ed' (which stands for elapsed days) instead of '7d'.

Apply the change

Press Enter. The task will now span exactly 7 calendar days continuously, ignoring non-working time.

Formatting Tip: Elapsed durations (ed, eh, em) are perfect for tasks that progress continuously without human intervention, such as concrete curing or shipping times.

Solution 2

Change Default Working Hours per Day to 24

Adjust the global calendar options if your resources actually work 24 hours a day continuously across the entire project.

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Frequently Asked Questions

Why does a standard day equal 8 hours in Microsoft Project?

By default, Microsoft Project assumes a standard working schedule of 8 hours per day (typically 8:00 AM to 5:00 PM with a one-hour break). The software uses this standard to translate days into hours for precise scheduling.

How do I check which project calendar is currently applied?

Go to the 'Project' tab on the ribbon and click 'Project Information'. In the dialog box that appears, check the 'Calendar' dropdown to see if your project is using Standard, 24 Hours, or Night Shift.

What is the difference between 'd' and 'ed' in Project duration?

The abbreviation 'd' stands for working days, meaning the software calculates the timeline based on your defined calendar working hours. The abbreviation 'ed' stands for elapsed days, which represents a continuous 24-hour block of time that ignores weekends and non-working hours.

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