Goal: Estimate task durations - Project

Warning: You are viewing this page with an unsupported Web browser. This Web site works best with Microsoft Internet Explorer 6.0 or later, Firefox 1.5, or Netscape Navigator 8.0 or later. Learn more about supported browsers.

Email this link

Printer-Friendly Version Bookmark and Share

Goal: Estimate task durations

Applies to
Microsoft Office Project 2003 Microsoft Office Project Server 2003 Microsoft Project 2000 and 2002

One of the best aspects of using Project is that it can calculate a realistic schedule for you, often based solely on task durations and task dependencies that you enter. Sure, you might have other scheduling controls, such as start (start date: The date when a task is scheduled to begin. This date is based on the duration, calendars, and constraints of predecessor and successor tasks. A task's start date is also based on its own calendars and constraints.) and finish dates (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.) and calendars (calendar: The scheduling mechanism that determines working time for resources and tasks. Project uses four types of calendars: the base calendar, project calendar, resource calendar, and task calendar.), but those are the exception, not the rule. Because a schedule's accuracy relies so heavily on accurate durations, spending a little brainpower on developing your durations (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.) will pay off.

Tip This article is part of a series of articles that describe a broad set of project management activities. We call these activities "goals" because they are organized around the project management life cycle: Build a plan, track and manage a project, and close a project. The project life cycle is outlined in The Project Map, where you can find a link to an article about each project management goal. Most of the articles include links to supporting information or procedures that you perform in Project or Project Server. These "goal" articles were designed to help you not only use Project but also better understand project management.

Previous goal Next goal

See all goals on the Project Map

number 1 Start with some basic research The information that can help you estimate how long certain tasks take to complete can come from several sources.

More . . .

Potential sources include:

Your own experience Draw on your own background from times when you carried out similar tasks in this or other projects.
The experience of your team members Consult with the resources who have been responsible for certain types of tasks. If you already have a team in place, have the members develop their own durations for their assigned tasks on this project; this can serve as a commitment from those responsible for completing tasks.
Previous projects Review projects that you or other project managers built and tracked. Any actual durations recorded will be especially helpful.
Industry standards and benchmarks Find duration information pertinent to your industry. In books, journals, and on the Web, you can find task lists with recommended durations. Professional organizations for your industry are also a good place to find information.

Build a time buffer into your project

Because you can't anticipate every issue that might delay your tasks, even the most accurate durations need a little "wiggle room." This provides a measure of risk management for your project. There are different ways to build a time buffer into your project:

Add a percentage to every duration If you think a task will realistically take 40 hours to complete, adding a 5% buffer (buffer: Additional time added to a task's or project's scheduled duration that accounts for possible increases in the actual time required to complete the task or project.) changes it to 42 hours. A 10% buffer changes it to 44 hours. Extra time is built into the schedule, just in case you need it. If you don't need it, this buffer can allow successor tasks to start earlier.
Add a buffer task Add a modest "buffer task" to every major phase of the project, or a sizable buffer task to the project as a whole. If you find that you need an extra day for a task that's slipping, you can remove the buffer task and add its time to the slipping task. Your overall finish date for the phase or the project will remain the same.

Number 2 Create a milestone When you want to identify a significant event in your schedule, such as the completion of a phase, create a milestone in your project.

Create a milestone

Number 3 Estimate durations You can model a project by using a what-if analysis to help you accurately estimate durations for your schedule and to simulate future resource loads and their effect on project timelines.

Estimate durations by modeling with a what-if analysis

Number 4 Enter a duration After you determine how long it will take to complete a task, it is time to enter a duration. Enter an estimated duration if you still aren't sure how long a task will take to complete.

Enter a duration

Number 5 Interrupt work on a task If two tasks occur simultaneously, you can pause the work on the task that starts first, begin the second task, and then start work again on the first task when the second is finished.

Interrupt work on a task

Number 6 Create a calendar To identify working and nonworking time for a specific task, create a calendar. For example, a piece of machinery needed to complete a task may be available only on certain days of the week. You can identify the working time on a task calendar, and the task is scheduled accordingly.

Create a calendar for a task

Number 7 Assign a calendar to a task After you create a task calendar, you apply it to the task or tasks that you created it for.

Assign a calendar to a task

Number 8 Add supporting information about a task Add more information about a task in the form of notes, documents, and links to Web pages.

Click all of the following that apply:

Insert an entire document into a Project plan, such as a report, letter, or other information, to help document your plan.
View and upload documents if you want to link supporting documents by using Project Server.
Insert a hyperlink to include a link to a Web page.
Add a note to tasks, resources, or assignments if you have only a small amount of information that you want to include directly in your project file.

Get Office 2007