Effort-driven scheduling

Add a second crew to a task in Microsoft Project and one of three things happens: the task gets shorter, the work goes up, or each person's share goes down. Effort-driven scheduling is the setting that decides between the first and the other two. It is useful when the work really can be shared, and misleading when it cannot. Owners meet it most when a vendor or contractor says that more people will finish sooner, and the schedule agrees a little too readily.

Learning outcomes

• Explain what effort-driven scheduling holds constant and when Project applies it.
• Predict what happens when you add a resource to a task under each task type, with effort-driven on or off.
• Set the Effort driven option for a task, show it as a column and set it for new tasks.
• Recognize tasks where adding people should not shorten the schedule, and set them up accordingly.

The lesson

What effort-driven means

An effort-driven task keeps its total work the same when you add or remove resources. Add people, and Project spreads the remaining work across them; remove people, and the ones left carry it [1][2]. Microsoft's example is a set of drawings that takes one drafter four weeks: with four drafters on an effort-driven task, Project schedules it for one week [2].

It sits on top of the formula from Lesson 13, Work = Duration × Units [3]. Effort-driven says: when the units change because people were added or removed, treat work as the thing to protect. What gives instead depends on the task type, which is why the two settings sit side by side on the same tab.

The first assignment does not count

Effort-driven calculations only start after resources are first assigned to a task [1]. The first assignment sets the work; later changes to the team redistribute it. That has a practical consequence. If you assign four installers to a 30-day task in one step, Project gives each of them the full 30 days and the work becomes 4 × 30 days of effort. Nothing shortens. If you assign one installer, then add three more in a second step, an effort-driven Fixed Units task drops to a quarter of the duration.

Same people, same task, different answer, depending only on whether they were assigned together or one at a time. When a resourced schedule produces durations nobody can explain, the order of assignment is one of the first things to check.

How it works with each task type

Microsoft's help sets out the combinations [1]. A Fixed Work task is always effort-driven: the check box is not available, because holding work is what Fixed Work means [1][3]. On a Fixed Units task, adding resources shortens the duration. On a Fixed Duration task, adding resources lowers each resource's units, so the same work is shared over the same days [1]. Summary tasks and inserted projects cannot be effort-driven at all [1].

Turn effort-driven off and the logic flips. Each new person brings their own work, so total work rises and the duration does not move. Figure 2 shows all five combinations for the simplest case: a task with one full-time person for 10 days (80 hours), to which a second full-time person is added.

View the data

Task type	Effort-driven	Duration after	Work after	Units each
Fixed Units	On	5 days	80 h	100%
Fixed Units	Off	10 days	160 h	100%
Fixed Work	Always on	5 days	80 h	100%
Fixed Duration	On	10 days	80 h	50%
Fixed Duration	Off	10 days	160 h	100%

Setting it

For one task, double-click it, select the Advanced tab of Task Information and select or clear Effort driven [1]. For the whole picture, right-click a column heading, choose Insert Column and add Effort Driven, a Yes/No field you can edit straight in the table [1][2]. For tasks you have not created yet, set the default in the Project Options dialog [2]: File > Options > Schedule, where the New tasks are effort driven check box sits beside the default task type for the file [4]. Check that box in every file you inherit. Do not assume it is on or off.

When you add or remove people on a task, Project usually shows a small Actions indicator next to the task. Its options let you choose, for that one change, whether to keep work and change duration, keep duration and change work, or keep both and change the hours per day. It is a useful override, but it changes only that edit. The task's settings stay as they were, so the next edit behaves the old way.

Screenshot to come

When more people should not mean less time

Effort-driven scheduling assumes work divides cleanly. Real work often does not. Microsoft's own counter-example is a one-week client review that takes a week however many clients attend [2]. On a building project the list is longer:

• Reviews and approvals. A consultant review period is a contractual clock, not effort.
• Inspections and witness tests. The fire alarm verification takes as long as the system takes to test, not as long as the number of witnesses allows.
• Space-limited work. Six installers cannot work in one aisle. Past a point, extra people get in each other's way.
• Single-path equipment. One crane, one hoist, one test rig. More people do not add a second one.

For these, use Fixed Duration with effort-driven off, or keep them unresourced. The aim is that a staffing change shows up where it really lands: in work and cost, not in a shorter bar.

Northgate worked example

Northgate Distribution Centre (fictional) is a 12,000 m² tilt-up warehouse in Vaughan, Ontario, for Northgate Logistics Inc. (fictional). Pallet racking is outside Halvorsen Builders' CCDC 2-2020 contract: it is the owner's separate contract, and it starts at milestone M10, racking and occupancy start, on Mon Jan 17, 2028, three days after M9, Ready-for-Takeover and Substantial Performance (see the Northgate fact sheet). Because it is the owner's own contract, the owner's master schedule, NDC_OwnerMaster_2027-01-11.mpp, carries it in detail.

The plan

The task is 9.5 Install pallet racking, with the generic resource Racking installer (RKI) set up in Lesson 16. The racking vendor's price is based on 960 installer-hours (illustrative). The scheduler sets the task to Fixed Work, enters 960 hours of work and assigns RKI at 400%, four installers, in one step. Project calculates 960 ÷ (4 × 8) = 30 working days. With Family Day on Mon Feb 21, 2028 as a non-working day on the Ontario calendar from Lesson 4, the task finishes Mon Feb 28, 2028.

The change

Northgate's operations team wants racking finished sooner so it can start receiving stock. The vendor confirms it can add two installers and work two aisles at once. The scheduler raises RKI's units to 600% in the Task Form. Because the task is Fixed Work, and so effort-driven, work stays at 960 hours: 960 ÷ (6 × 8) = 20 days. The task now finishes Fri Feb 11, 2028, 10 working days earlier.

Now suppose a different scheduler had left the task on the default Fixed Units with effort-driven off. Adding the same two installers would keep the 30-day bar and raise work to 1,440 hours. The schedule would show no time saved and 480 hours that the vendor never priced. Both answers come from the same edit (Figure 3). Only one matches what the vendor said.

View the data

Case	RKI units	Work	Duration	Start	Finish
Plan	400%	960 h	30 days	Mon Jan 17, 2028	Mon Feb 28, 2028
Fixed Work (effort-driven)	600%	960 h	20 days	Mon Jan 17, 2028	Fri Feb 11, 2028
Fixed Units, effort-driven off	600%	1,440 h	30 days	Mon Jan 17, 2028	Mon Feb 28, 2028

The check the software cannot make

The Fixed Work answer is only right because the vendor confirmed two aisles can be worked at once. If the racking had to go in one aisle at a time, six installers would not finish in 20 days, and the honest model would be a longer duration or a lower productivity, not a cleaner bar. The owner's scheduler records the vendor's confirmation in the task's Notes field so the next reviewer knows why the duration dropped.

Screenshot to come

Owner's move

• Ask for the Effort Driven column. When a contractor's or vendor's resourced plan arrives in Project format, show Type and Effort Driven next to Work. A schedule that shortens every time a crew is added deserves questions.
• Tie any "more people, less time" claim to a reason. Space, sequence and equipment decide whether work divides. Record the reason in the task notes.
• Switch it off for clocks. Reviews, inspections, notice periods and cure times should not shorten because a name was added.
• Assign the team in one step when the team is known. It keeps the first-assignment rule from producing odd durations, and makes the work number the one you meant.
• Watch the Actions indicator. Pick the option that matches the real change, and remember it applies to that edit only.

Common mistakes

1. Assuming effort-driven applies to the first assignment. It does not. The first assignment sets the work; only later changes redistribute it [1].
2. Turning effort-driven off and then "crashing" with resources. The work rises, the dates do not, and the cost report shows hours nobody agreed.
3. Leaving effort-driven on for reviews and inspections. A second reviewer halves a contract review period on paper and nowhere else.
4. Looking for the check box on a Fixed Work task. It is greyed out because Fixed Work is always effort-driven [1].
5. Trusting the Actions indicator to change the task. It changes one edit. The task's type and effort-driven setting stay as they were.

Quick quiz

1. On an effort-driven task, adding a resource keeps which value constant?

   1. Duration
   2. Total work
   3. Each resource's units
   4. The finish date

2. When do effort-driven calculations start?

   1. When the task is created
   2. When the baseline is set
   3. After resources are first assigned to the task
   4. Only when the project is levelled

3. You add a second resource to an effort-driven Fixed Duration task. Project:

   1. Halves the duration
   2. Doubles the work
   3. Lowers each resource's units
   4. Changes the task to Fixed Work

4. Why can you not clear Effort driven on a Fixed Work task?

   1. Fixed Work tasks are always effort-driven
   2. It is only available in Project Professional
   3. The task must be manually scheduled first
   4. Fixed Work tasks cannot have resources

5. Northgate's racking task is Fixed Units with effort-driven off, 4 installers, 960 hours, 30 days. Two installers are added. What does Project show?

   1. 20 days, 960 hours
   2. 30 days, 1,440 hours
   3. 30 days, 960 hours at 400%
   4. 45 days, 1,440 hours

Show answers and explanations

1. B. Effort-driven tasks keep total work at its current value and spread it across the resources [2].
2. C. Effort-driven calculations apply only after the first assignment [1].
3. C. On Fixed Duration tasks, more resources lower each resource's units [1].
4. A. Project always treats Fixed Work tasks as effort-driven [1][3].
5. B. With effort-driven off, each new installer brings their own work: 6 × 8 h × 30 days = 1,440 hours, and the duration is unchanged.

Key terms

Effort-driven scheduling

Keeping total work constant when resources are added to or removed from a task.

Effort Driven field

A Yes/No task field that turns effort-driven scheduling on or off for a task.

First assignment

The assignment that sets a task's work. Effort-driven redistribution applies only to changes after it.

Actions indicator

A small prompt Project shows after some edits, offering a one-time choice of what to keep constant.

Crashing

Shortening a task or project by adding resources, usually at extra cost.

References

1. Microsoft. Change the effort driven setting for task types. Microsoft Support.
2. Microsoft. Effort Driven (task field). Microsoft Support.
3. Microsoft. Change the task type for more accurate scheduling. Microsoft Support.
4. Microsoft. Application.OptionsSchedule method (Project). Microsoft Learn, Office VBA reference (EffortDriven and TaskType arguments map to the Schedule tab of Project Options).

Verified on November 6, 2026.

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