From the course: Microsoft Project 2019 Essential Training

Understand duration, work, and units

From the course: Microsoft Project 2019 Essential Training

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Understand duration, work, and units

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- [Instructor] A task's duration, work, and assignment units are interconnected. The mathematical relationship is simple, and it's the key to getting your resource assignments right every time. First, let's go through a couple of definitions. Duration is the length of a task from its start to its finish. If a task starts on Monday morning and ends on Friday afternoon, the duration is five workdays. Work represents the person-hours it takes to complete the task. If a task has a duration of five days, but you're going to spend only 10 hours on the task, the work is only 10 hours. Assignment units, also referred to as units, are the percentage of the assigned resource's available time dedicated to the task. Full-time is 100%, half-time is 50%. You can show units as a decimal, too. In that case, full-time is 1.0, and half-time is 0.5 Basic algebra is all it takes to understand the relationship between duration, work, and units. Duration is equal to work, divided by units. Suppose you estimate work at 40 hours, and you specify that the resource works on the task 50% of the time. Doing the math gives you a duration of 80 hours, which is the same as 10 full workdays. So, the duration is 10 days. Switching the formula around, work equals duration, multiplied by units. If you estimate duration to be five days, and the resource works 40% on the task, the work is two full workdays, which is 16 work hours. Similarly, Project calculates units if you give it the duration and the work. Say you set the work at 40 hours and the duration at four weeks, that's 160 work hours. The percentage of time the resource works on the task is 25%, shown here as 0.25. Project has built-in rules about which values it calculates. Unless you give Project specific instructions, the program tries to calculate duration first, then work, and finally, as a last resort, units. If you fill in project, work, and units, the program will calculate duration. If you fill in only work, Project still calculates duration by filling in the units cell with 100%, or the resource's maximum units. Say you fill in duration and units. In that case, Project calculates work. If you fill in only duration, Project calculates the work by filling in the units cell will 100%, or the resource's maximum units. If you give it both duration and work, Project will calculate the units. By understanding how duration, work, and units are connected, you can assign resources and get the results you want.

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