If you've ever managed a project before, you might have used the Iron Triangle and not even know you did. For a seasoned project manager, this is the keystone to managing your projects. The iron triangle, also known as triple constraint, project management triangle, or flexibility matrix, models the constraints project managers work within on every project they oversee. The balance of costs, time, and scope all affect the quality of a project.
Costs This is the financial constraint on a project, also known as your budget. Costs could represent resources as well as materials. Or any other financial item that is required to accomplish the project. Once you've established a budget, the project manager's role is to keep the project within budget. Unless you have an unlimited budget, you want to make sure costs are controlled.
Time This is your project completion date or "live" date. It involves managing the time each of your tasks needs to be completed. A project schedule is usually created with tasks, along with start and end dates. If using the waterfall approach, they are typically in order in which things need to be completed.
Scope This constraint consists of all the tasks or deliverables within the project. It may be one of the hardest to control. Once a project is started, things come up, or new requirements emerge. A client may ask for a small change here and a slight change there. Although these requests may be small by themselves, if you keep adding small changes, they can end up changing the overall scope of the project. We call this scope creep.
So how do you manage these three constraints? Let's say your project is due on June 1st, and all parties have agreed on the date, the scope of work, and the budget. A new request was made to make a significant change to the scope of work. To keep this triangle in balance and not negatively affect the final product's quality, a decision will need to be made. If this scope change is necessary, something else has to change along with it. Do you push the date (time) out to July 1st to complete the additional work? Or do you add more resources/people (costs) to get the job done by June 1st? As you can see, if you change one aspect of the triangle, you will need to adjust one of the other sides of the triangle. Otherwise, you may not be satisfied with the quality of the completed work.
Written by David Singletary
If you need help managing a project contact me at firstname.lastname@example.org