Project Management: The Triple Constraint

Like any human undertaking, projects need to be performed and delivered under certain constraints.  We must be successful in delivering on project scope given a finite amount of time, under a certain budget, and with a limited amount of human and technical resources.  


Traditionally, these constraints have been listed as "scope," "time," and "cost”.  These are also referred to as the project management triangle, where each side of a triangle represents a constraint. One side of the triangle cannot be changed without affecting the others. A further refinement of the constraints separates product "quality" or "performance" from scope, and turns quality into a fourth constraint.

• The time constraint refers to the amount of time available to complete a project
• The cost constraint refers to the budgeted amount available for the project
• The scope constraint refers to what must be done to produce the project's end result

These three constraints are used to illustrate that project management success is measured by the project team's ability to manage the project, so that the expected results are produced while managing time and cost.  


These three constraints are often competing constraints: increased scope typically means increased time and increased cost, a tight time constraint could mean increased costs and reduced scope, and a tight budget could mean increased time and reduced scope.  If there is a requirement to shift any one of these factors then at least one of the other factors must also be manipulated.


One of the first tasks a project manager of a brand new project is faced with is the prioritization of the Triple Constraint. This can only be done by communicating with the client. Whether the client understands project management or has ever heard of the Triple Constraint, in their mind, they already know what is most important to them. They may require that the project be completed within a certain timeframe, no matter the costs.  Or, they may require that the project stay under budget, no matter how long it takes to accomplish.  And, typically, the client requires that the project finish on time and within budget, delivering on all the scope and quality aspects set forth in the project charter.  Your job, as project manager, is to find this out, and to manage to these priorities.