What Is the Triple Constraint Theory in Project Management?

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Photo by Octavian Dan

There are three widely known key elements crucial to reaching the successful completion of a project. The three aspects that make up the classic Triple Constraint Theory in project management are time, cost and scope, all of which are interrelated and linked to one another.

But did you know the PMBOK 4th Edition expanded the Triple Constraint Theory to include three additional factors? As projects become more and more complex, there are more connections between components and, as a result, more constraints to consider. Before delving into those newer elements, let’s cover the core three triple constraints of project management.

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The Original Three Aspects that Make Up the Triple Constraint Theory


Ideally, all tasks on a project will be completed and delivered on time. Tasks are time-bound activities and should be scheduled and assigned according to the number of resources required to complete the task. At the beginning stages of a project, a schedule is created that includes deadlines for when objectives are to be met.


The cost constraint is the estimated amount of money required to successfully complete a project. A significant portion of costs goes towards resources. These are tangible and intangible assets, such as acquiring services or getting people on board of the project.


The depth, reach and accuracy of the project must be thoroughly defined to achieve final objectives. The scope will have a direct impact on the quality of output. Starting on the wrong foot with an unclear scope can result in unexpected or undesirable outcomes.

The Triple Constraint Theory is often demonstrated in the form of a triangle. Each constraint is assigned to an inner angle of the triangle to demonstrate that one constraint cannot be changed without affecting at least one other constraint. The shape connects the three constraints to signify their interdependency and complete integration. The center point of the triangle represents the balance of all three constraints.

For example, if time increases, adjustments may have to be made to cost or scope. Likewise, if scope increases, time or cost and maybe both will be affected. When considering these aspects, especially when planning for a project, it is important to consider what trade-offs you are willing to make as the project progresses. This way, the project manager and stakeholders have a clear understanding of project priorities.

If you are already well aware of the above three constraints, you can dig deeper into the following less known, less straightforward factors. These additional three aspects to consider along with the classic triple constraints of project management are quality, resources and risk.

The Six Constraint Theory?


This constraint relates to the scope of the project but focuses more on the characteristics of a deliverable. If a project is flexible and provides a permissible range of quality for a certain item, then that project has quality tolerance. Essentially, this constraint forces you to consider whether you will settle for lesser quality when your first choice is no longer available. This constraint often suffers when time or costs are strained, resulting in the compromise of quality.


As a general rule, the more resources acquired, the higher the costs. In some cases, however, money may not be a solution to fixing every problem. For example, if a required resource won’t arrive on time to meet your deadline, throwing more money into the situation might not necessarily fix your problem.


A well-developed plan considers potential risks on a project and outlines zero-tolerance risks, if any, that would lead to the failure of the project. When it comes to risks, project managers often examine the probability of risks and their repercussions and the degree of willingness to accept these potential consequences.

A project is considered high-risk when any of these factors are not managed well or are not executed according to the project plan. It is of the utmost importance that the project manager manages and moderates triple constraints to prevent any slippages or hiccups during the course of the project to ensure quality results are delivered. And if you find your plan veering off the tracks, it’s time to reflect and modify your project baseline.

Criticisms of the Triple Constraints of Project Management

While the above factors are likely to be a part of every project, some argue that the Triple Constraint Model is no longer useful. One argument is that time and cost cannot be measured on the same plane since cost represents a fixed factor (money), whereas time is relative. The total amount spent on a project is the same as on another project, but a significant delay in one project would differently impact another project.

Another issue with the Triple Constraint Theory is that cost and time are too basic for determining the project’s value. One project might be completed on time and within budget but might have less value for the business than a project that was completed both over time and budget.

These criticisms may seem to outweigh the effectiveness of applying the triple constraints of project management. That being said, it is not that any of these constraints are irrelevant; rather, they may be too simplistic for some projects. The Triple Constraint Theory was expanded for a reason, that reason being that the three classic categories are much too broad when there are so many other factors that come into play on a project. Also, most people aware of the Triple Constraint Theory are project managers themselves, meaning that everyone else on the team may not be familiar with the Triple Constraint Theory and, as a result, not be able to apply its methods.

Although constraints are a huge part of your project, it still makes up only a fraction of the work expected of a project manager. Using time management software can help you stay organized and track your schedule to stay on top of the time constraint, in turn helping you keep up with all of the other constraints. actiTIME is a tool for project managers and teammates.

Originally published at actitime.com

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