Change a task duration

These instructions are specific to Microsoft Project 2016, 2013, and 2010.

You can change a task’s duration at any time to reflect the actual amount of time it needs.

  1. Click View > Gantt Chart.

  2. In the Duration column for the task, type the duration in minutes (m), hours (h), days (d), weeks (w), or months (mo).

  3. If the new duration is an estimate, type a question mark (?) after it.

  4. Press Enter.

Be careful about changing a duration by using the Start and Finish columns, especially for linked tasks or automatically scheduled tasks. Your changes might conflict with the task dependencies or task constraints Project is tracking, which can throw a carefully constructed schedule off track.

Also in this article

Change a summary task duration

Use estimated durations

More about task durations

Change a summary task duration

You can change the duration of a summary task the same way you change a regular task. But be careful — changing the duration of the summary task doesn’t necessarily change the durations of the subtasks.

On the Gantt Chart, a summary task bar always shows the summary task duration (black line) and the sum of the durations of its subtasks (blue bar), like in the picture below. You can see the difference between the two at a glance.

Image of a summary task that is longer than its subtasks

Use estimated durations

Is the question mark disappearing when you try to add an estimated task duration? Estimated durations are probably not turned on for your project. To turn them on:

  1. Click File > Options.

  2. In the Project Options dialog box, click Schedule.

  3. Scroll down to the Scheduling options for this project area.

  4. Select the Show that scheduled tasks have estimated durations check box.

    Options dialog box, Schedule tab, scheduling options for this project area

More about task durations

These instructions are specific to Microsoft Project 2007.

Enter or change task duration

  1. If the task you are entering the duration for is not currently listed in the project plan, add the task to your task list. If you are entering or changing the duration for an existing task, skip this step.

    How do I add a new task?

    1. On the View menu, click Gantt Chart.

    2. In the Task Name field, type a task name at the end of the task list.

      You can insert a task between existing tasks by selecting the row below where you want a new task to appear. On the Insert menu, click New Task and then type the task name in the inserted row. The task IDs are automatically renumbered after you insert a task.

  2. In the Duration column for the task, type the duration that you want.

    You can enter durations in minutes (m), hours (h), days (d), weeks (w), or months (mo).

  3. If the new duration is an estimate, type a question mark after it.

  4. Press ENTER.

Tip: To change the one-day default value, on the Tools menu, click Options and then click the Schedule tab. Clear the New tasks have estimated durations check box.

Tip: To express the durations of new tasks in units other than days, on the Tools menu, click Options and then click the Schedule tab. In the Duration is entered in box, select a duration unit.

Notes: 

  • When you change a task's duration to meet a specific target, be sure that the change still reflects realistic time requirements for the task. Be sure to also check and adjust the corresponding amount of work that is assigned, as necessary.

  • Some projects may not use estimated durations. If your project does not use estimated durations and you type a question mark in the Duration column for a task, the value is not considered an estimation. To allow estimations in your project, on the Tools menu, click Options, and then click the Schedule tab. Select the Show that tasks have estimated durations check box.

  • If you are changing a duration and the new duration uses a different unit from the existing duration, you must first do the calculation separately and then enter the new value. There is no automatic conversion. For example, if the current duration for a task is 1 day, and you want to change the duration to reflect hours instead of days, you must first calculate the number of working hours in a day on your own and then enter the new value in hours.

  • Summary tasks (sometimes called "hammock tasks") cannot be edited directly. To change a summary task, change the subtasks that make up the summary task.

Increase the accuracy of your estimates

To increase the accuracy of your estimates for task duration, use your own past experience and the past experiences of others who have done something similar in previous projects. Ask questions such as:

  • How long did the task take?

  • What were some of the challenges you encountered?

  • What would you do differently if you had to do it over again?

Note any differences between the new task and similar tasks done in the past, and take into account those differences when you estimate a task's duration.

Include the following considerations as you estimate task durations:

  • Durations can depend on the experience of the resource who performs the task. A highly experienced resource can sometimes complete certain tasks more quickly than a less experienced resource.

  • Estimates should be revisited when the work starts. You will know more about the tasks at that point.

You can also derive your estimates by comparing optimistic, pessimistic, and expected durations. This is sometimes called a PERT analysis.

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