project management triangle

Understanding the project management triangle

Reading time: about 6 min


  • Strategic planning

Here's a term you may have never heard of but probably know a lot about: the project management triangle.

If you've ever heard the phrase "quick and dirty" mentioned at work, then you are more familiar with the project management triangle than you might think. The project management triangle refers to the three main constraints: time, scope, and cost. Every project involves these three pillars to some degree, and they are all interrelated. For example, a project that is "quick and dirty" is often done for low cost over a short period of time, but the scope of what's required is limited.

The triangle goes by many names, including the iron triangle, the triple constraint triangle, and the iron triangle theory. All of the terms are meant to describe the main task of project management: keep a project on time, in scope, and under budget by making tradeoffs between the three constraints.

One of the necessary skills of an effective project leader is that they know how to navigate the three constraints to produce the best results possible. 

The triple constraints of the project management triangle 


The first constraint, time, describes how long you have to complete a project. This includes the time you need to kick off an assignment, get a proof-of-concept approved, and actually launch a product. More often than not, projects are short on time—an assignment that should take six months may need to be completed in half the time. This is often due to a specific event or milestone, and that's typically one of the constraints you have to navigate. 

For example, a company may need to launch a platform by a certain date to capitalize on Cyber Monday shopping. In that case, the timing is not adjustable, and the project has to stay on track.

Project managers often solve time constraints by expanding their work capacity. This may mean bringing on extra developers to build a platform more quickly or hiring more writers to populate a new blog with content faster. However, this is often only possible when there's flexibility in one of the other main pillars: cost.


The cost to complete a project is typically the most constrained pillar in the project management triangle. Few projects have an unlimited budget, and it's typically the job of the project manager to keep a project on or under budget.

A variety of factors can impact cost. If a project goes off schedule, that can heavily impact the budget because you have to pay people for a longer period of time to complete the work. Expanding the scope can also affect cost. There are likely more costs associated with the additional requirements if there's more to do. Constantly shifting KPIs can also heavily impact the budget. Whenever the team has to go back to the drawing board, they are accruing additional costs to make it to the finish line.

One of the ways to navigate this pillar is to manage the third part of the triangle. If you can keep a project within a tightly defined scope, you can keep your costs to a minimum.


Scope is the parameter of a project: what needs to be delivered, how it needs to be delivered, and to whom it must be delivered. The scope is often outlined at the beginning of a project, and it helps orient team members to the desired end result. Think of scope as the goal posts in a football game: your scope is clearly defined and located in the end zone. 

Now imagine if the goal posts constantly changed. Every time you moved forward 10 yards, the goal posts moved back or to the left or right. This is what is known as scope creep. It's when the end result of the project changes or expands in the middle of production. Scope creep is challenging because as the goals shift or expand, they often cause a setback in time, cost, or both.

If you're taking an agile approach, your scope is likely changing often. In these situations, your time and costs are fixed, which means you have to define your scope wisely to make sure it doesn't break your other constraints.

The benefits of using the project management triangle 

While it may sound like the project management triangle is tough to navigate, it can help you manage your projects more successfully. Knowing that most challenges in a project come down to cost, scope or timing can help you quickly identify which parts of the project are under pressure and which parts can be leveraged to relieve that pressure.

Think about managing a website. There are often updates that need to be made to capitalize on events throughout the year. Holiday shopping, for example, might trigger a request to update the website's search capabilities, e-commerce features, or blog content. That will require time, resources, and a well-defined scope to make the most of the opportunity, and it has to fit in among other business priorities.

Using our Cyber Monday example, if a team is working on re-launching their website to better accommodate Cyber Monday traffic, they have to meet a fixed deadline. The project manager may choose to kick off the project early, so they have plenty of time to meet the deadline without straining the budget to get the work done. But let's say the project was deprioritized for a while because a few more urgent projects came up along the way. Knowing the time, cost, and scope constraints means a project manager will know how long they can leave the project on the back burner before the timeline or scope is at risk.

Taking the project management triangle to the next level

There is a way to make the project management triangle work harder for you. Visualization tools can help project managers identify where there's flexibility in each of the three constraints and the limitations. A PERT chart, for example, can help determine priorities and ensure the projects that have more stringent time constraints take precedence. A Gantt chart can alert you to dependencies that may need to be completed to ensure your timeline isn't thrown out of whack. And virtual whiteboards can help facilitate decision-making, so your projects stay on track.

The important thing to remember is that projects don't function in a vacuum. The main takeaway from the project management triangle is that every constraint impacts the project as a whole. There has to be some give and take for projects to come together which is why team collaboration is so important. Having a shareable tool that quickly displays vital project information means that everyone becomes responsible for the project's health, and managers can quickly identify challenges and opportunities well in advance.

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