Fixed work and fixed duration are common measurements used in assessing the time budgeted in project management. The primary difference between these terms is that work is normally measured in hours, while duration is measured in days. If you plan a whole day to work a task, for instance, the duration is one day and the work is eight hours.

Fixed Work Basics

Fixed work is the actual amount of time that you plan for a task in a project. Your fixed work plan allows you to decide how much labor and resources to allocate toward a task. Knowing a task will take four hours using a piece of equipment helps you plan how to use the equipment before and after that task. Fixed-work plans also allow you to figure out the costs of labor per hour, which is a gauge of production efficiency.

Fixed Duration Basics

Duration generally is used to gauge the long-term implications of completing one project. If you know it will take six weeks for a particular project or set of tasks, you can more effectively plan for other projects before and after that. Effective planning also allows a company to develop and implement long-term strategies by taking into account the duration of completing certain projects in pursuit of long-term objectives.

Fixed-work Task vs. Fixed-duration Task

If you plan a fixed-work activity, you dictate how many days it will take or should take to complete a task. You then build in the necessary people and resources to ensure project completion occurs within that time. When you set a fixed-duration task or activity, the amount of people and resources included in the activity don't impact the timeline. If you give a work team one week to complete certain tasks toward a project, each person carries out their roles over the course of that week.

Change Impact

When you make changes to a project, the impact on duration and work varies. With fixed work, since you allocate a certain number of hours to an activity, the implication of change is minimal. If you delay a project or expedite it, the amount of hours need for a task within the project remains constant. However, if you change the duration of an activity, the amount of work changes. If you shorten the duration, for instance, you have to allocate a higher number of hours and resources to it quickly.