Triple Constraint: Using PSM software to conquer the Iron Triangle

By Mark Engelberg, TimeLinx Software


All projects have constraints. Adhering to those constraints will ultimately determine the success of your project. What is known as the Iron Triangle or the Triple Constraint is a combination of three factors that are dependent on one another. The three factors are Scope, Time, and Cost. These need to be in constant equilibrium to measure changes that must be made while still keeping the project on track. Why do they need to be in balance? Because ultimately, at the center of your Triangle (or as one of the constraints) is Quality. To maintain your expected level of quality of delivery, you cannot sacrifice any constraint without impacting the others.

Having the correct PSM software to ensure your Triangle is kept in balance makes this easy. But as you’ll read further on, the need to be agile in project delivery today often means stretching the three sides of the Triangle while still maintaining your usual quality of delivery.

What is the Triangle?

Here are the definitions:

The Scope is a written and precise description of the deliverables of your project. The vaguer the Scope, the more challenging it becomes to deliver work and agree with your stakeholders as to progress and ultimately that your work is completed. Assuming a known and agreed Scope, it would then appear that delivering the entire Scope would seem like you can say your project was successful. But of course, that’s not entirely true. If providing the work took longer than planned or promised, will your customer be happy? They got what they expected, but it took weeks (or months or years) longer than initially scheduled. Hence, the second constraint is:

Time (or Schedule). The Time is set in the planning phase and is your estimate of how long your effort will take to do this work. It is an estimate based on the number of tasks, their complexity, the number of resources (people) needed to do the job, and an understanding of obstacles that may appear in this particular project or type of project. You will set a date when your customer will be looking for the work.

If the customer asks for additional work, then your deliverables will change. And it is likely the Time to deliver that work will be longer and the date will be pushed out. But that is all OK if the customer wanted it and you have software that can help you re-align the resources you will need. The customer will expect to pay for additional work, and you will negotiate that amount. However, if you failed to define the Scope initially, you will have a problem with a customer who expected additional work that you didn’t specify and now does not want to pay for it. Now you are out of balance with the following constraint, which is:

Cost (or Budget). It should be evident that if you require more Time to deliver, this will require additional manpower. And more hours. Or resources with different skills that may have a higher cost. But manpower costs money. You either have more hours being spent or more costly resources being used. Either way, without negotiation with the customer, your project is in trouble as someone will need to absorb the cost difference.

How Does the Triangle Work, and how does PSM software play a part?

The three constraints must be measurable with your software, so you know the status of each one in real-time. And it should be obvious now how all three of these factors are tightly connected. When you build your Scope of Work (SOW), you expect that the work will take a certain amount of time being performed by people with specific skill sets, hence the Cost to you because you pay people for their time.

Notice that there are two versions below of the Iron Triangle. in the two diagrams below, one Triangle shows Quality as one of the factors while the other Triangle has Scope. In general, using Quality as a constraint isn’t really practical as who wants to reduce quality in the delivery of the other three sides. But you can see that changes in any of the factors affect the other two whereas an impact on Quality is always a result if you can’t keep all of the constraints (whether you think of it as 3 or 4 constraints) in balance.

When any of the factors changes, the other two will also change to keep the total of the Triangle at 180° (remember trigonometry class?). You will have choices to make (often not good ones) about how you resolve this dilemma.

Project and Service Management software should be able to keep track of each of these in real-time. If the Cost of a deliverable goes up, you need to know immediately. Equally, if a task is taking longer than scheduled or budgeted for, you need to be able to manage expectations and deal with appropriate agility. Because the Scope can change (either intentionally or unintentionally), all constraints will change (other than Quality). They will need to be updated (hopefully automatically with PSM software) as the project progresses. Keeping abreast of these changes and making sure that everyone involved is aware of them at all times will give your team the ability to implement agility against a seemingly immovable concept.

Stretching the Iron Triangle and being Agile

Although the Iron Triangle is named because any break in its factors will result in project failure, it can be stretched. The concept of agility is necessary and applicable in today’s enterprise environment. To change Scope, Cost or Time on the fly is possible with good management (note that Quality is not assumed to change). But to do this, you must be on top of absolutely every update on every aspect of every project. Because of this, some players in project management believe the Triangle is no longer applicable or possible. “Agility” is today’s buzzword, and this is incompatible with what some consider a stifling and outdated concept. In truth, the idea can be reframed to match today’s requirements, but to do so, you will need a flexible and agile PSM solution.


Although some may think of the Iron Triangle as outdated, it is still relevant in today’s corporate environment, albeit with a few adjustments. Executive sponsorship or leadership is one of the most influential vectors in the success of a project and plays an essential role in the maintenance of the Triangle. To be a good project manager, you need to measure every aspect of a project, including how every individual is delivering. After all, it is individuals who are responsible for whether a project succeeds or fails. And the best way to keep abreast of project success on an individual level to maintain agility as well as maintaining the Triangle? A good, integrated PSM solution, of course.

# # #

About TimeLinx
TimeLinx delivers innovative project & service management software as a complete solution that perfects the sell-track-manage-support-bill cycle that services organizations must have to delight their customers; TimeLinx brings the cycle together in a single application that offers less frustration, better project management, complete reporting, and improved profitability – all specially designed for Infor and Sage.