While the concept of the triple constraint triangle, or iron triangle of project management, is not a new one, it is one of the most important theories in the field. Understanding the key components of the triangle and how they interrelate can make the difference between project success and failure.
Below, we take an in-depth look at the three sides of the project management triangle, what it means, and how you can apply it in your day-to-day management of projects.
Introducing the project management triangle
Did you know that the project management triangle has been around since at least the 1950s? Over the years it has gone by many names, including:
- Project Management Triangle
- Iron Triangle
- Project Triangle
- Triple Constraint Triangle
Despite its age, the triangle remains a vital concept in project management, as it helps illustrate the importance of properly managing project constraints.
In project management, constraints are any limitations that are placed upon the project. These are restrictions that the project manager and team must work within. While there can be many constraints on any project, there are three universal ones that every team must face.
- Time constraint: This refers to the pressure to meet a project’s schedule for completion. It includes major milestones, the deadlines for each project phase, and the date for delivery of the final product.
- Scope constraint: The scope of a project creates bounds around what a project is meant to deliver. It defines specific goals, deliverables, functions, and features, as well as the tasks needed to complete the project.
- Cost constraint: This constraint limits the expense of a project. Often called the project’s budget, it comprises all of the financial resources available to complete the project on time, within its predetermined scope. The cost constraint includes money for materials, labor, vendors, quality control, and more.
It’s important to understand that each constraint is intertwined with the other two. For example, decreasing the project budget will likely result in a change in scope and potentially a schedule shift. Increasing the scope would likely increase the cost and lengthen the time to complete the project.
A common saying that illustrates the interdependence of the iron triangle is “cheap, fast, or good — choose two.”
Some versions of the triangle also add quality in the center of the image to illustrate that properly balancing the three constraints will impact the quality of your project. For instance, if you try to deliver too much in too little time with too little budget, your quality will suffer.
There have also been attempts to innovate or improve on the triple constraint in project management, including a six-sided alternative. But, the original idea is still the one most widely followed and recognized.
A deeper look at the triple constraints
Before we discuss how to best manage the triple constraints on your projects, let’s take a deeper look at each side of the triangle.
The time constraint is all about completing your project deliverables on schedule. Successfully completing a project within the given time restrictions requires proper scheduling and effective time management.
By definition, a project must have a concrete beginning and end. In other words, as soon as a project is initiated, you and your team have time constraints you must work within. Typically there are specified dates you meet for key project deliverables. There may also be significant progress milestones you’re expected to achieve.
If your project doesn’t stay within the expected time constraints, it means late deliverables and upset customers. It also often means budget overruns (impacting your cost constraint) as you likely have more labor hours than originally expected.
This is why time management is one of the six primary functions of project management. It’s critical for project success that a project manager works within the given time constraints to accomplish the project on schedule.
Project scope encompasses all the work that must be done to deliver an end product that meets the required functions and features of the customer. The project scope generally includes what goes into a project and what factors define its success. It typically consists of the functionalities and specifications outlined in the product requirements documentation.
Having a defined scope helps ensure that the end deliverables meet the expectations of the customer. However, it also creates constraints around what can and cannot be included in your project.
If the project work starts to expand beyond the original scope, without proper change control and customer approvals, it’s called “scope creep.” Generally, if the project features grow beyond the original plan, it means spending more time and money to complete it. Plus, your customer may not want extra features and functionality, especially if it impacts usability.
Scope management, another one of the six primary project management functions, is vital to ensure your project scope doesn’t grow out of control. It also helps ensure you don’t underdeliver a product missing key requirements or functionality requested by the customer.
No project has an unlimited pool of funds. Even on a “time and materials” project, where you are reimbursed for labor and material costs, you will have cost restraints. Typically, a client will expect a project estimate upfront and require support for any expenses that go over that amount.
Your project budget will usually outline the cost restraints you must work within. This may include both fixed costs (such as quoted vendor contracts) and variable costs (including your team’s labor). It may also include a contingency buffer for mitigating risks. Project budgets may also include expected revenue and predicted profit.
Effectively managing your project costs is essential for ensuring you don’t run out of money before the work is completed. You may also have profitability goals you’re expected to meet. For instance, your business might require that all projects be completed for at least 20% less than the sale price.
Cost management, another primary project management function, helps ensure your project doesn’t go over budget. It includes not only controlling project costs but also efficiently estimating and allocating them.
What is the triple constraint triangle in Agile?
The project management triangle was introduced long before some of the newer project management frameworks were created. So, it’s natural to wonder if it can still be applied when using newer methods such as Agile.
Often, in traditional project management, the three constraints (scope, time, and budget) were defined at the beginning of the project. Agile, on the other hand, uses an iterative approach that allows these project components to evolve.
But, while the approach is different, the triple constraints of project management still apply. Agile simply turns the triple constraints upside down.
While Agile is designed to let projects involve as they progress, it still sets and follows constraints within each sprint or phase. Each iteration has defined time and costs, and its scope is generally adjusted to enable the team to accomplish the highest priority work given the time and budget available.
Also, while Agile projects may have more flexible timelines and budgets, they still don’t have unlimited time and money. So, managing the tradeoffs between constraints is just as relevant and important as for traditional projects.
How to apply the triple constraint triangle
Successful project management requires effectively managing the tradeoffs between the three sides of the project management triangle.
The value of the triple constraints in project management is that it serves as a visual reminder of the impact decisions will make on other parts of your project.
It’s critical to plan, manage, execute, and monitor a project’s cost, schedule, and budget. But, if the three are done in isolation, decisions may be made that unwittingly impact other areas and the overall quality of the project.
To apply the triple constraint triangle effectively, you need to manage your three areas of constraint in an integrated way. By using time and materials software, you can instantly see how changes to one component of the triangle will impact the other two.