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Iron Triangle

The Iron Triangle is a fundamental aspect of how we understand success in a project (Pollack et al., 2018). It is a representation of the most basic criteria by which project success is measured. The concept of the Iron Triangle is an effective way of communicating the interrelationships between these central success criteria. Movement of one criterion, for example, in response to client demands or resource limitations, can put pressure on the other criteria. Failure in one constraint will likely lead to negative pressure on one or both of the other two (Mokoena et al., 2013, p. 814). This is sometimes expressed as “good, fast or cheap – pick two” (van Wyngaard et al., 2012, p. 1993). Effectively managing the Iron Triangle has been found to be central to project success, however, it has also been found that research into the Iron Triangle is “[…] one of the most overlooked fundamentals of project management” (van Wyngaard et al., 2012, p. 1997).

The Iron Triangle has been wildly used in literature since the 1970s. Next to that the field of project management has wildly changed over the years. A valid question to raise is if the Iron Triangle still is valid. Pollack et al. conducted a research in 2018 to test the validity of the Iron Triangle in the modern day & age.

Over time the vertex of quality has been under grave discussion. Alternatives as Scope, Performance or Requirements have been proposed. The research of Pollack et al. (2018) has shown that quality is still the right vertex to be used. The concepts of time, cost and quality are highly integrated concepts in the field of project management. The conclusion of the researchers is that two different perspectives are concerned with the Iron Triangle.

The first perspective focuses on the triangle being the representation of the status of the most important project success criteria. Regarding this perspective the authors note:

From the perspective of viewing the Iron Triangle as a representation of the status of the most important project success criteria, this paper would argue that the relevance of Time, Cost, Quality, or any other criteria is entirely contingent on the context. The only persistent criteria by which the success of all projects can be assessed are client and contractor satisfaction with the outcomes and impacts of a project.

The second perspective views the Iron Triangle as a didactic device. The intent is to communicate the relationship between Time, Cost, and other potential criteria. Given the didactic perspective, Quality could be replaced by Scope, Performance, Requirements. It all depends on the kind of project being assessed.

However, the authors conclude:

Upon reviewing the network diagrams that were created for Time, Cost, and Quality, it is clear that these three concepts are highly interconnected. In comparison, Scope does not occur in any of these networks. Requirements and Performance do appear in these networks, but their presence is inconsistent, and of a lower significance than Quality. Both of these concepts appear more linked to Quality, than either Time or Cost. Time, Cost, and Quality are so consistently interconnected in the literature that it is not surprising that the Iron Triangle has emerged as a distinct and significant concept in the project management literature.


Mokoena, T., Pretorios, J. and Van Wyngaard, C. (2013), “Triple constrain considerations in the management of construction projects”, Proceedings of the 2013 IEEE International Conference on Industrial Engineering and Engineering Management, pp. 813-817.

Pollack, J., Helm, J., & Adler, D. (2018). What is the Iron Triangle, and how has it changed? International Journal of Managing Projects in Business, 11(2), 527–547.

van Wyngaard, C., Pretorius, J. and Pretorius, L. (2012), “Theory of the Triple Constraint – a conceptual review”, Proceedings of the 2012 IEEE International Conference on Industrial Engineering and Engineering Management, pp. 1991-1997.

Iron Triangle