Enter or change a task duration

When you initially create a new task, Project 2007 gives the task an estimated duration (duration: The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.) of one day. You can modify the estimated task duration to reflect the actual amount of time that the task requires. You can modify your estimate at a later time; however, it is best practice to hone your estimation skills so that your initial project plans are realistic for your organization.

 Tip   Changing the task duration is one method that you can use to help meet your finish date (finish date: The date that a task is scheduled to be completed. This date is based on the task's start date, duration, calendars, predecessor dates, task dependencies, and constraints.), resolve any resource overallocations (overallocation: The result of assigning more tasks to a resource than the resource can accomplish in the working time available.), cut costs (cost: The total scheduled cost for a task, resource, or assignment, or for an entire project. This is sometimes referred to as the current cost. In Project, baseline costs are usually referred to as "budget."), increase the scope (scope: The combination of all project goals and tasks, and the work required to accomplish them.), or increase the quality (quality: The degree of excellence, or the desired standards, in a product, process, or project.).

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 (optimistic duration: The best-case possibility for the total span of active working time expected for a task, that is, the amount of time from the optimistic start to optimistic finish of a task.), pessimistic (pessimistic duration: The worst-case possibility for the total span of active working time expected for a task, that is, the amount of time from the pessimistic start to pessimistic finish of a task.), and expected durations (expected duration: The total span of active working time expected for a task, that is, the amount of time from the expected start to the expected finish of a task.). This is sometimes called a PERT analysis (PERT analysis: PERT [Program, Evaluation, and Review Technique] analysis is a process by which you evaluate a probable outcome based on three scenarios: best-case, expected-case, and worst-case.).

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.

ShowHow 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.

  1. 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).

  1. If the new duration is an estimate, type a question mark after it.
  2. 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.


  • 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.

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Applies to:
Project 2007