Amal Nagm

A task's duration is the amount of time you expect it will take to complete the task. Project 2007 can work with task durations that range from minutes to months. Depending on the scope of your project, you'll probably want to work with task durations on the scale of hours, days, and weeks.

For example, a project might have a project calendar with working time defined as 8 A.M. through 5 P.M. with a one-hour lunch break Monday through Friday, leaving nonworking time defined as evenings and weekends. If you estimate that a task will take 16 hours of working time, you could enter its duration as 2d to schedule work over two eight-hour workdays. By starting the task at 8 A.M. on a Friday, you should then expect that it wouldn't be completed until 5 P.M. on the following Monday. No work would be scheduled over the weekend because Saturday and Sunday have been defined as nonworking time.

Tip You determine the overall duration of a project by calculating the difference between the earliest start date and the latest finish date of the tasks that compose it. The project duration is also affected by other factors, such as task relationships. Because Project 2007 distinguishes between working and nonworking time, a task's duration doesn't necessarily correlate to elapsed time.

Tip You can schedule tasks to occur during working and nonworking time. To do this, assign an elapsed duration to a task. You enter elapsed duration by preceding the duration abbreviation with an e. For example, type 3ed to indicate three elapsed days. You might use an elapsed duration for a task that you don't directly control but that nonetheless is critical to your project. For instance, you might have the tasks Pour foundation concrete and Remove foundation forms in a construction project. If so, you might also want a task called Wait for concrete to cure because you don't want to remove the forms until the concrete has cured. The task Wait for concrete to cure should have an elapsed duration because the concrete will cure over a contiguous range of days, whether they are working or nonworking days. If the concrete takes 48 hours to cure, you can enter the duration for that task as 2ed, schedule the task to start on Friday at 9 A.M., and expect it to be complete by Sunday at 9 A.M. In most cases, however, you'll work with nonelapsed durations in Project 2007.

Project 2007 uses standard values for minutes and hours for durations: one minute equals 60 seconds, and one hour equals 60 minutes. However, you can define nonstandard durations for days, weeks, and months for your project. To do this, on the Tools menu, click the Options command, and in the Options dialog box, click the Calendar tab, illustrated here.

You should consider two general rules when estimating task durations.

For your real-world projects, you will often estimate task durations. Good sources of task duration estimates include:

For complex projects, you probably would combine these and other sources to estimate task durations. Because inaccurate task duration estimates are a major source of risk in any project, making good estimates is well worth the effort expended.

One general rule of thumb to consider is called the 8/80 rule. This rule suggests that task durations between eight hours (or one day) and 80 hours (10 working days, or two weeks) are generally sized to a manageable duration. Tasks shorter than one day might be too granular, and tasks longer than two weeks might be too long to manage properly. There are many legitimate reasons to break this rule, but its guidelines are worth considering for most tasks in your projects.