The Triple Constraints

By Eddie Merla, PMP ® 

The triple constraints for projects are: the project requirements (scope), the schedule, and the costs (or budget) for the project.  Once you have established these three parameters for a project, they become the baseline for the project and can be used to determine variance.  There is also a direct relationship among these three constraints.  If you increase scope, you most likely will have to extend your schedule and increase your budget.  If you decrease your budget, you most likely will have to reduce your scope.  If you shorten your schedule, you will either have to cut back on your scope, or add resources, thereby increasing your budget.

When do these constraints become established for a project?  Well, it depends.  The project methodology for an organization will determine when these constraints become established.  Typically, “ballpark” estimates of scope, cost & schedule are determined during the initiation of a project. “Baselines” for scope, cost, and schedule would typically be established through the planning processes.

Can baselines be changed?  Yes, of course.  Formal project methodologies usually allow formal changes to project baselines through change management procedures.  The PMBOK® identifies these processes in the “Monitoring and Controlling” process group. 

FYI, sometimes the triple constraints are also called the “project triangle” or the “iron triangle.”

The triple constraints become formalized through the planning processes and ultimately become the three primary baselines:  the Scope baseline, the Schedule baseline and the Cost Performance baseline.

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© 2010 Eddie Merla, PMP®

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Duende Project Management Services, a provider of Project Management Training and PMP® preparation products.  http://www.pmstudyproducts.com