Using Assumptions and Constraints for Realistic Project Planning

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Image of darts on a dartboard representing the need to not make project assumptions.

Few projects begin with absolute certainty. If absolute certainty was an "absolute" requirement, few projects would ever get off the ground. That's why "assumptions" and "constraints" are so important, used as key defining factors to ensure timely, realistic project results. Read on to learn more.

As projects are planned and executed, some facts and issues are known, others must be estimated. Estimation is an art, with many fine points to finesse between certainty and wishful thinking. You can't just hope you have the resources needed to do the job, and you can't just wait until every resource is available to begin.  Instead, you must take proactive steps to manage and mitigate using informed assumptions and constraints.

Assumptions = Possibilities. Constraints = Limits.

Assumptions and constraints form a foundational basis for project planning, filling in the gaps between known proven facts and total guesswork.

Each assumption is an "educated guess", a likely condition, circumstance or event, presumed known and true in the absence of absolute certainty. Each constraint is a limiting condition, circumstance or event, setting boundaries for the project process and expected results.

Aside from the consequences, effective planning demands that varied types of assumptions and constraints be considered, as illustrated in the following list:

What are the possible assumptions and known constraints regarding.....?

  • THE EFFORT: The estimated tasks and activities required to manage the project and produce deliverables.
  • THE SCHEDULE: The estimated tasks and events needed to complete the project.
  • THE RESOURCE POOL:  The estimated staff resources needed to complete the project.
  • THE BUDGET: The estimated cost of the project, allocated to tasks, resources and phases.
  • THE CONTRACTS: The anticipated performance of contractors, vendors and suppliers.
  • THE PROCESS: The use and applicability of available management standards.

As assumptions and constraints are defined (as discussed below), each of the "types" listed above must be considered to ensure both comprehensive results and realistic approaches.

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Assumptions and Constraints "To-Do List"

Identification is the first step in planning and managing known "assumptions and constraints".

Identify and Challenge - As assumptions are identified, each must be viewed with an appropriate degree of skepticism. Assumptions cannot be mere guesswork or wishful thinking.

  • For example, you can't just hope that the budget will be sufficient, you have to examine and verify budget estimates to get as close to certainty as possible.
  • In turn, constraints must also be viewed skeptically, with an eye towards possible elimination. Constraints pose restrictions, and any relief from these restrictive elements would be welcome.
  • But, if constraints cannot be eliminated, then appropriate workarounds must be developed.

Assumptions should be evaluated from a long term perspective.

Evaluate - Analyze according to confidence level (i.e. How confident are you that this assumption will be proven correct), followed by a related "if-then" risk counterpart analysis (i.e. If this assumption is proven incorrect, what will be the likely consequences for the project?).

  • During the course of this analysis, the "impact of the incorrect assumption" must be determined. Impact can be weighed at various levels, from serious (threatening successful or timely project delivery), to moderate (absorbable impact on deliverables, schedules or costs), to minor (insignificant impact on deliverables, schedules or costs).
  •  Depending upon the assessed confidence level and related impact, a full risk assessment may be required. If you have high degree of confidence that a given assumption is true, then further analysis may be unwarranted. Lower confidence and higher impact would probably require further analysis and the related risk assessment.

In contrast, constraints must be evaluated from a short term perspective, according to immediate impact - i.e. How does a given constraint limit or refine the project in one or more respects? For example, product availability constraints can impact multiple elements of a single project. Product delays can elongate the project schedule, add to costs, and negatively impact resource availability. As constraints are assessed, all points of impact must be determined.

Once assumptions and constraints are identified and assessed, they must be incorporated into the relevant portion of the project plan.

Incorporate - Assumptions, combined with known facts, will drive the formation of the project plan, providing the actionable basis (albeit with varying degrees of certainty) for planned tasks, schedules, budgets and resource assignments.

  • Constraints must be factored into the project plan from the start in the form of stated "workarounds".
  • These workarounds will mitigate constraint "impact" by providing the means for the project to move ahead despite the existence of constraining factors (i.e. A schedule change allows for concurrent, non-dependent work to proceed even if there are delays in product delivery. This scheduling workaround will prevent an overall schedule delay).

Unidentified constraints will not just disappear, they will likely pop up at some later point as full fledged project problems. Consider this example: You are working on a project where specialized technical skills are required. You estimate that these specialized resources will be required for (40) hours per week during the month of June, and you prepare your project plan based on this assumption. However, you fail to account for the fact that these resources will only be available for (20) hours per week in the month of June. Initially, this resource limitation was a constraint, but since it was not identified at the outset, once June rolls around, it becomes a major problem.

Initial assumptions and constraints are rarely static.

Control - As the project evolves, assumptions will be proven true or untrue. Changing circumstances may eliminate or modify previously identified constraints. In either case, you must be prepared to react, with contingencies, workarounds and modifications to plans and deliverables.

  • To ensure a constant state of readiness, identified assumptions and constraints must be tracked and monitored throughout the project process.
  • In addition, assumptions can be factored into the plan via checkpoints (i.e. the point at which the assumption will be tested (proven correct or incorrect (in part or whole). These checkpoints can then be monitored to ensure that working assumptions are valid, and if not, to take corrective action.

Once a project is complete, assumptions and constraints should be reviewed as part of an overall "post-project" review process.

Review - To evaluate all steps taken for identification, assessment, incorporation and control.

  • Standardized project reviews incorporate "assumptions and constraints" considering quality, accuracy, effectiveness, and omissions (missed assumptions and/or constraints that should have been discovered as the project began).

From project initiation through closure, established assumptions and known constraints set the stage for project planning and execution. As the project proceeds, assumptions and constraints will be used to define and shape tasks, schedules, resource assignments and budget allocations. In this manner, each identified assumption and existing constraint forms a framework to be used to manage an otherwise uncertain future, laying out a roadmap for how the project will proceed.


If you're looking for a fast, easy way to achieve project planning success, you'll find it inside the Fast Track Project Toolkit. This unique, informative online course gives you everything you need to become a project leader and fast tracking expert. Here's what you'll learn:

  • How to plan and govern projects using strategic project fast tracking.

  • How to use strategic project fast tracking to save time and make the most of available resources.

  • How to use strategic fast tracking to overcome project constraints and limitations.

  • How to use strategic fast tracking to negotiate with stakeholders and build shared expectations.

  • How to use strategic fast tracking to become a more productive project manager and team member.

Source: Unless noted otherwise, all content is created by and/or for

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Right Track Logo staff writers have experience working for some of the largest corporations, in various positions including marketing, systems engineering, help desk support, web and application development, and IT management. is part of Right Track Associates, proprietors and publishers of multiple web sites including, Fast Track Manage, HOA Board List and more. We started in 2001 and have continued to grow our web site portfolio, Toolkit products, and related data services. To learn more, visit us at Right Track Associates.

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