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Project Management Triangle (Time-Cost-Quality)

The Project Management Triangle, also known as the Iron Triangle or the Triple Constraint, is a model that outlines the interrelated constraints of time, cost, and quality that govern any project. The triangle serves as a framework to understand how changing one constraint inevitably impacts the others. Here's a brief description of each corner of the triangle:


This refers to the schedule or timeline allocated for the completion of the project. Time management in a project involves setting milestones, deadlines, and the sequence of tasks. Shortening the project's timeline often results in increased costs or compromises in quality.


Cost refers to the budget allocated for the project, encompassing labour, material, equipment, and other expenses. Lowering the budget could lead to compromises in quality or delays in the project timeline.


Quality is the standard or level of excellence the project is expected to meet. This could relate to functionality, reliability, durability, performance, and other relevant quality metrics. Increasing the quality typically involves more time and/or higher costs.

Balancing the Triangle.

The Project Management Triangle illustrates that you cannot change one corner of the triangle without affecting the other two. For example:

  • If you want to accelerate the project timeline (Time), you might need to allocate more resources, increasing the Cost, or you might have to compromise on Quality.
  • If you want to decrease Costs, you may have to extend the Time required to complete the project or sacrifice Quality.
  • If you aim to enhance Quality, you could incur additional Costs or need more Time to meet the higher standards.
The triangle serves as a visual aid for project managers to make informed decisions and for stakeholders to understand the trade-offs involved in any project. Achieving the right balance between time, cost, and quality is crucial for project success and often involves making difficult decisions based on priorities and constraints.

Origin of the Project Management Triangle (Time-Cost-Quality)

The concept of the Project Management Triangle, also known as the Iron Triangle or the Triple Constraint, is often attributed to Dr. Martin Barnes, a British engineer and management consultant. He introduced the concept in the 1960s as a way to help project managers understand the interrelated constraints that they must balance when overseeing a project.

However, it's important to note that the concept of balancing competing project constraints is likely much older, even if not formalised in the triangular model we recognise today. The triangle has become a staple in project management literature and is taught as a foundational principle in the field. It has also evolved over time, with some modern variations incorporating additional factors like scope, resources, or risks, thus extending it into more complex models.

The Project Management Triangle is widely used in various industries to help teams understand the trade-offs between time, cost, and quality, and to make informed decisions accordingly.
Trevor O'Sullivan

Trevor O'Sullivan

General Manager. Since the early 2000s, Trevor has worked with thousands of Talent Management professionals to develop and apply assessment-based talent management solutions for selecting, developing and managing people. Trevor is an active member of the TTI Success Insights (TTISI) Global Advisory Council, contributes to TTISI product development and is a regular presenter at TTISI-R3. He is honoured to have received multiple Blue Diamond Awards and, more recently, the Bill Brooks Impact Award recognising his contributions to the TTISI global network.

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