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Project constraints

Understand and critically discuss the importance of the constraints that project managers must operate within when delivering projects.

With any project, some limitations and risks need to be considered and addressed to ensure the project’s ultimate success.

The scarcity of available resources for completion of any project gives us triple constraints: a deadline, a budget, and at least a minimum acceptable level of performance (Atkinson, 1999). Project managers refer to these as time, scope and cost. These are frequently known as the project iron triangle and constitute a fundamental ‘framework for evaluating competing demands’ (Project Management Institute 2013).

Failure to understand these constraints correctly and effectively is enough to doom any project, even if all other aspects are done perfectly.

Project constraints are illustrated by a triangle formed of time, scope and cost at a corner each. This shows that the project is constrained by the availability of each of these factors. Changing one of them will impact on the others.

The triple constraints of project management:

  • The time constraint refers to the project’s schedule for completion, including the deadlines for each phase of the project, as well as the date for the rollout of the final deliverable
  • The scope of a project defines its specific goals, deliverables, features and functions, in addition to the tasks required to complete the project. One could say that the scope clearly expresses the desired final result of a project.
  • The cost of the project, also known as the project budget, comprises all of the financial resources needed to complete the project on time, in its predetermined scope. Keep in mind that cost does not just mean money for materials – it encompasses costs for labour, vendors, quality control and other factors.

These three constraints work in tandem with one another. Project managers can trade between these three constraints, however, changing one will impact the other two points.

Why is the iron triangle important? These triple constraints indicate the key factors that both define the framework of a project and direct project managers as to where adjustments would have to be made if one or another of those constraints became problematic.

For example, if your project is running behind schedule, you can work to reduce the features of the project which means reducing scope. Then you can dedicate more resources to moving the schedule ahead and by doing so, increasing cost. You can also, if possible, change the due date to give the project team more time. This balancing of the three elements allows for the successful planning, resourcing and execution of a project. These are the critical elements of a successful project, and these are the things that will determine whether you have successfully managed a project.

Your task

Read ‘Six (yes six!) constraints: an enhanced model for project control’ by Jay M. Siegelaub and discuss what further constraints project managers should consider when managing and delivering projects.


Atkinson, R. (1999). Project Management: Cost, Time and Quality, Two Best Guesses and a Phenomenon, it’s Time to Accept Other Success Criteria. International Journal of Project Management, 17(6), 337–342

Project Management Institute. (2013). A Guide to the Project Management Body of Knowledge (PMBOK Guide). (5th ed.).

© Coventry University. CC BY-NC 4.0
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Foundations of Project Management

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