Microsoft Project – Understanding Duration, Work and Units

When you are dealing with projects in Microsoft Project, you are dealing with the fields; Duration, Work and Units. You must have to understand what are these fields and how these will behave during the project schedule for successful Schedule Management in Project.

These fields are connected. Hence, when we modify one field’s value, will reflect the change in another field’s value. The whole project schedule (and cost) is depending on these fields.

Microsoft Project calculates these fields in the order; Duration first, next Work and then Units.

As these are connected fields, we represent them using the below formulas. We will discuss more of these fields, below;

1. Duration = Work / Units

When you start a Task, it has a definitive Start & Finish dates; we can call it a length of a Task or a Duration. It is a length of a Task in Work time.  Also, it depends on the number of resources you use for the Task. Hence, when we represent this in a formula; it is a Work divided by Units.

For example;

From the above table; observe that the fields are connected. When we assign 2 persons (2 Units – 100% each) to a Task, Duration was recalculated; also observe that Duration was recalculated based on the given Work time.

Usually, we represent Duration in ‘days’.

2. Work = Duration * Units

How many hours do you need to complete the given Task? This is what Work represents. Multiplication of Duration and Units will tells us, the number of person-hours we need to complete the Task. You can see the above table for examples.

Usually, we represent it in ‘hrs’.

3. Units = Work / Duration

This represents the % of the available time for the resource, assigned to the given Task. It is the division of Work by Duration. Let’s look at this from the above table;

From Project’s Gantt Chart view; we can see “Duration” and “Work” fields. And, “Units” field we can see in Task details.

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