The project management “triangle” of scope, time, and cost has been informing projects ever since the first team member was hired to accomplish a job. In the basic setup of a triple constraint, one of three elements (or possibly more) can constrain a project. The elements are budget/cost, time/schedule, and scope. If a change is posed to any one of these elements, something else must change.


In the modern corporate landscape, a project is typically “bound” or constrained by three elements, which may be expressed in different ways. The triple constraint theory, also called the Iron Triangle in project management, defines the three elements (and their variations) as follows:

  1. Scope, time, budget
  2. Scope, schedule, cost
  3. Good, fast, cheap

While the names of the three elements of the triangle may change, they all measure essentially the same thing: a fixed budget, a fixed schedule or timeline, and a fixed set of expectations or deliverables.

The triangle comes into play when something affects one of its “legs.” If that happens, you may need to adjust one or both of the other elements to accommodate the change. For example, if a client suddenly shortens a time frame, then a project will likely need more resources, or perhaps a scope reduction.

In another case, a company may have two competing projects, but not enough staff to fully support both. A project manager may then need to move employees from the first project to the second, which affects either the scope of the first project, or the timeline, or both. In other words, a project manager can make these changes, but something’s got to give.

The concept of “quality” is sometimes introduced as another factor in the project constraint triangle, or as a fourth “leg” in what would be a project diamond. However, there are varying views on this, as quality is subjective. Does the quality of a less-in depth web page suffer, or can it still be a high-quality page with reduced scope? These are questions a project manager must always consider and keep in mind during conversations with stakeholders and clients.

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