Triple Constraint

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Big Idea

Also named The Iron Triangle

During projects, hard decisions have to be made by trade-offs among the objectives of the project. The simplest objectives are time, cost and quality (TCQ). These three objectives form the iron triangle. Projects will position themselves in either one corner or sometimes between two corners. The project lies where the objective is a constraint e.g. EU-research funding is limited to a certain cost.

Harvey Maylor consider an example in his book Project Management of the relation between the objectives. In a research project, you have limited time to do and finish the market report. When the project starts, you are able to plan the project to end on the designated date. The quality of the project relies on the spent time, and thus, will the final results do. Very little time is allocated to this project so that limits your work. However, you can add more resources to the project but that costs you money.

This example show the relation between the TCQ objectives and if one is fixed then you have to make trade-offs between the other two if you want the project to change in one of three directions. Hence, trade-offs are so called priority of the project’s objectives. In projects, it can be necessary to make a compromise. For instance, you can’t spend any further financial resources and have to either delay the project or accept lower quality of the product.

The Iron Triangle

The book Power of Projects engages with the project triangle an idea almost in line with the iron triangle. The three corners are defined as time, resources and deliverables which can be aligned to time, cost and quality. The interdependence is described by, when deliverables are changed you visualize that you drag the deliverables’ corner in the triangle, thus will one often two of the other corners get a new angle. One objective can’t change without changing the others. As a result, the project manager and the team has to be aware of the relation between the objectives – awareness of the consequences of trade-offs so to say.

To delve further into defining the three main objectives, conformance and performance are tools Harvey Maylor engages with. Giving the project reliability, conformance is defined by asking, can the project be guaranteed to deliver on time, within the budget and meet required quality? Conformance set the frame whether the project can fulfill the planned schedule, budget and deliverables. Performance shows whether the project actually fulfil the objectives. Maylor describes for example, that the project manager try to get low-cost suppliers to keep the cost at the minimum (performance) but the fact that it is actually happening in practice has to be ensured by the manager (conformance).


TCQ apply to almost every single project due to the principles of project management. It is therefore an essential tool in project management. Especially in the early stages by defining the project and its measurements. Though, as well is the iron triangle applied throughout the project while new issues and problems occur.

Awareness of the trade-offs between the three parameters are important to complete a successful project. The conformance part will be the first to initiate to uncover where the constraint(s) is/are. Perhaps they are given beforehand. The performance is the essential work to secure that the objectives are met or making reasonable trade-offs if the project manager can sense that the constraints is changing.


Harvey Maylor comes up with an additional fourth objective to the triangle – scope or requirements. For limitations see article “Limitations of the iron triangle”. He states that the TCQ objectives aren’t necessarily known in the beginning of a project. Since requirements vary during a project’s life cycle there can’t be only three measures. Therefore, scope, that encompasses the requirements of the project, has to be a possible constraint as well. For example, external stakeholders can change their requirements during the project eventually affecting one or more of the three other objectives.

Annotated Bibliography

Maylor, H., 2010, Project management

The paragraph about the iron triangle display real world examples of the relation between the three objectives and what trade-offs there can be made during a project’s life cycle. He questions whether it is reasonable to exclude them in some occasions due to contemporary emerging project management principles. He does as well engage with their impact but also the possibility of not knowing them in initial project phases.

Attrup, M. L., and Olsson, J. R., 2013, Power of Projects

They deal with the project triangle similar to the iron triangle but delve into the role of its role in goal setting in projects. By presenting clearly how one objective impacts others the reader get a good understanding of the importance of applying the project triangle I project management. Further underlined by the importance of renegotiation of the project triangle while changes occur during the life cycle. The book give comprehensive overview of how to apply the project triangle in projects.

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