Project assumptions: Understanding their role and significance in project management

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What are you assuming right this second? Lots of things! At a minimum:

  • That your chair will hold you up (or maybe that your standing desk won’t collapse)

  • That your internet connection will remain mostly problem-free

  • That your company will not close its doors tomorrow

We all make assumptions about the world around us — it’s a part of navigating a complex and sometimes chaotic world. What good would we be in everyday life if we constantly doubted that gravity would hold us down, that electricity would keep working, and so on?

We do the same thing in projects: we make certain project assumptions so we can focus on the less certain stuff between those assumptions.

Of course, assumptions aren’t always correct, and that’s where things start getting tricky in the project management realm.

Here’s what you need to know about project assumptions — including what to do when assumptions are wrong.

What are project assumptions in project management?

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Project assumptions in project management are the elements that project managers and teams assume to be true for the purposes of planning and executing a project. It isn’t possible to account for every variable — no matter how unlikely — when building a project plan. 

Project assumptions help us focus on the right variables by assuming the answers to others and walling them off from consideration.

The Project Management Institute (PMI), in its formal definition of the term, adds that project assumptions should be considered true “without any empirical proof or demonstration.” These assumptions should be listed in the project management plan, usually in a scope document.

Examples of project assumptions

Building an effective project plan and a realistic project schedule requires some degree of faith or certainty: that your team will work at the same pace they typically do; that your company and industry will continue to exist; that the global supply chain won’t grind to a halt. 

Of course, these elements don’t always turn out to be true. But if one fails, you’ll probably be heading back to the drawing board for the project anyway — so it’s safe (ish) to go ahead and make the assumption as you plan the project.

Here are a few good examples of project assumptions your agency might make:

  • Material and resource costs will remain stable over the course of the project.

  • The project scope will not change in unmanaged ways.

  • Resource allocation and/or staffing levels will not be cut during the project.

  • Your team members have the necessary skills to complete their tasks at the needed level of quality.

  • Your office/facilities will remain operational (e.g., assuming no acts of God destroy or damage your building).

  • The industry you serve will not experience catastrophic changes or losses.

  • Resources will be available when scheduled (e.g., not overbooked with overlapping projects from multiple clients).

Why are project assumptions important?

Project assumptions matter because you need the ability to plan and make decisions — something that can’t happen well when you’re questioning everything.

Consider these three reasons why project assumptions are important, even helpful.

Foundation for planning

Some project assumptions give you a foundation for planning by ruling out the technically possible but highly unlikely scenarios. Other project assumptions provide a different kind of foundation for planning: they broadcast that we have a gap in information or even a known risk (see next section), and we’re assuming x. If y happens, we’ll know we need to reexamine our plan.

In both of these ways, project assumptions help set the stage for project strategy and execution.

Risk management

Project assumptions also help kickstart the risk management process. 

Assuming disaster won’t strike is nearly required for building a good project plan and schedule. But disasters do strike — and you can’t have a plan to mitigate them until you identify them as possibilities.

By identifying your assumptions and then tracking them over the course of a project, you’ll have an easier time seeing some potential risks coming. They’ll show up as assumptions that aren’t holding up, and because you’re watching for those exact elements, you’ll see them earlier and (hopefully) avoid getting blindsided.

Enhanced decision-making

Last, assumptions can provide a basis for better-informed decisions across all phases of a project — as long as your project assumptions are well founded and clear.

By removing peripheral issues and “what ifs” from the decision-making process, you gain clarity and focus that generally lead to better decisions.

Project assumptions vs. risks, dependencies, and constraints

Though there can be some overlap and interfacing, project assumptions are distinct from several other project elements. Let’s look at the differences between project assumptions and risks, dependencies, and constraints.

Project risks

Project risks are any circumstances or events that aren’t guaranteed to happen but that could affect the project, usually (but not always) negatively. 

Some project risks are also project assumptions (or the opposite of an assumption): project assumptions about undisrupted supply chains turned out to be wrong in nearly every industry back in 2020, and nearly every industry experienced closely related risks.

You want to identify project risks for similar reasons to why you identify project assumptions: Once you know what your risks (and assumptions) are, you’re in a better place to see when risks are becoming reality (or when assumptions aren’t).

Project dependencies

Project dependencies are tasks and activities that cannot move forward without others starting or finishing. You can’t build the email campaign (or anything, really) until the logo is designed and approved, so there’s a dependency built into any task or deliverable containing a logo.

These relate to assumptions in that your project schedule must be built in a way that can logically work (logo this week, poster next week) — but it’s an assumption that the logo will finish on time, and a risk that it won’t.

Project constraints

In any project, there are typically three constraints: project budget, project timeline, and project resources. These are the most basic parameters and limitations for building a project schedule, and they can also become both assumptions and risks. 

How should assumptions be documented in a project plan?

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Project management best practices include documenting everything — including your project assumptions. Here’s how to do it.

Create a dedicated section for assumptions

Don’t leave your assumptions unstated or scatter them across your project plan. Instead, create a specific section in your project documents (we recommend an assumptions log within the scope document) where you collect them. Doing so is crucial for organization and clarity: all project stakeholders (presuming they read the document) will see exactly what you’re assuming.

Categorize assumptions

Not all assumptions carry the same weight or matter equally to all stakeholders and project team members, so categorize your assumptions (for example, into categories like resources, timelines, and technology). 

Doing so will allow those responsible for specific areas to see the risks most relevant to them, lending greater clarity.

Link assumptions to project elements

Along similar lines, many project assumptions aren’t universal; they apply to one phase or one deliverable or one department. Instead of including all assumptions as a general group, link them to specific project elements where possible. Doing so helps everyone understand the specific impacts and relevance of each assumption.

Evaluate impacts of assumptions 

Similar to how you evaluate risk impacts, consider what it would mean if an assumption turns out to be incorrect. For example:

  • What risks does this assumption imply? 

  • What would you need to do to mitigate those risks? 

  • What contingency plans or alternatives are there?

Review assumptions after project completion

Assumptions also give us a great opportunity to learn lessons in one project that can help us with future projects. As a part of project closure or a project postmortem, make sure to review the project’s assumptions, noting which were correct and which failed.

Where assumptions failed, you’ll also want to note the impact of the failure(s) and what the team did to overcome or redirect. 

This crucial postmortem step helps your agency learn from history and improve its project management practices for the future. 

Document your project assumptions easily with

Project assumptions are key throughout the project planning process, helping teams and key stakeholders prepare for the potential impact of one of those educated guesses falling through.

But as your project progresses, it’s easy to lose sight of those assumptions if they aren’t documented in some way (like a project assumption log). 

Keeping up with these (as well as numerous other elements, like workflows, project objectives, and project risk management) requires careful focus and attention to details — and it’s a lot easier when you’re using the right tools. is an all-in-one platform that’s perfect for managing, streamlining, and optimizing every aspect of client work, including creating and managing all your project documents. With templates that can help you document project scope statements, project assumptions logs, and everything else you need to achieve project success, is the missing piece in your project management puzzle.

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