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The Iron Triangle of Project Management

One way or another, you will inevitably encounter the “iron triangle” concept in project management. This is, after all, one of the basic tenets of project management and, thus, a fundamental topic covered in project management courses.

What is the iron triangle, and why does it matter in project management?

Project management constraints

Projects will always have constraints. These are factors or variables that could limit your project in one way or another. For instance, unless you are wealthy and don’t have to think about money at all, you probably will have no choice but to work within your predetermined budget when building your dream house.

In other words, how much money you can spend on your house-building project will put a constraint on it. It will influence which materials you will use, which professionals you hire, and how many people will work on the construction.

Apart from money, other constraints will be the availability of the people who will work on your project. The more people working on your project, the faster you will build your house. Moreover, the more considerable their expertise, the better the quality of the finishing, masonry, joinery, and other project components.

Likewise, the availability of the equipment and materials your project needs could also impact your project. For instance, if you are using imported lumber and its shipment gets delayed, that will inevitably stall your project.

The triple constraints theory

The triple constraints theory is one of the more popular frameworks that project management professionals can use to make sense of project management constraints. The iron triangle concept arises from this framework.

According to the triple constraints framework, there are three significant constraints that project managers have to balance constantly. These are:

1. Time

How long do you have to finish your project? What is your project timeframe and schedule? That is the constraint of time.

An emptying hourglass on a table to measure time which is part of iron triangle in project management.

2. Cost

How much can you spend on the project? What is your budget? That is the cost constraint.

3. Scope

What is the expected output of the project, and what are its features? What are the project inclusions? That is the scope constraint.

These three constraints are connected, and together, they limit the project or mark project boundaries. Thus, a project cannot violate these constraints.

In other words, if you have a set budget, time, and scope, your project will have to fall in line to succeed. If any of these changes, you will have no choice but to adjust one or both remaining factors.

Thus, the triple constraints are often drawn as a triangle. (i.e., the iron triangle). Each of the three constraints represents a side, and the area defined by these sides is the project bound or controlled by these constraints.

Competing demands

Under the triple constraints model, the triple constraints of time, cost, and scope are competing factors. It is a project manager’s responsibility to balance them to accomplish desired ends and achieve project success.

Going back to the example given earlier, suppose you wish to build a 2,200-square-foot house with 2.5 baths and four bedrooms. Upon discussing your requirements with your architect and contractor, you came up with a cost estimate of USD 330,000, which is in the ballpark of the national average of USD 100-200 per square foot. Likewise, you have agreed that the whole project would take around seven months from permitting to completion.

While the construction is underway, you decide to have a walk-in closet. You also just found out that you’re expecting a new family member. Therefore, you want to outfit one of the rooms as a playroom and another as a nursery. Finally, you are resolved to upgrade flooring to parquet in the bedrooms and glazed ceramic tiles with inlays in the foyer.

All of these mean you’re changing the project scope. Since the constraints are interconnected, this change in scope has consequences on your time and cost constraints.

Specifically, adding a walk-in closet and a playroom plus changing your flooring to more luxurious options will inflate your project cost beyond the USD 330,00 you originally allocated. Likewise, since your upgrades require extra work, you will need to add to your timeline. Thus, your scope changes also mean a change in your project schedule.

In other words, complicated projects will naturally cost more and take longer. Likewise, if you have a fixed budget, you will have to adjust your scope (i.e., downgrade your materials) and time (hire fewer people and extend the target end date).

As a project manager, your goal is to balance these constraints and decide which of the three conditions will set the benchmark for the other two.

Beyond the triangle

The triple constraints theory — a.k.a. the iron triangle — provides project managers a handy way of assessing competing project constraints. However, experience will tell you that time, cost, and scope are just three potential constraints. There’s a lot more.

As a project manager, you need to study, go beyond the iron triangle, learn all other constraints, and find a way to balance all of these to end your project successfully.


Author Bio

Jerrin Samuel is the Executive Director at Regional Educational Institute (REI) in Abu Dhabi. Since 1995, REI has been at the forefront of education by delivering quality corporate training courses in the UAE, helping many businesses and organizations achieve greater productivity and higher customer satisfaction levels.


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