Successful project managers juggle three core aspects of every project — cost, time, and scope — to move everyone toward the next big deadline. The triple constraintproject management triangle is a model that helps you visualize this process and make it a reality. 

Much like the three sides of a triangle, these three factors, also known as “constraints,” have to be balanced if you want to cultivate a successful project.

Today, we’ll be digging into what a project management triangle is, its key benefits and challenges, and how to use it to increase the quality of the project, no matter how big or small it is. 

The project management triangle is made up of three project constraints: Cost, time, and scope. It’s a model that helps you understand each individual constraint and even more so, the way they’re interconnected, with the goal of maxing out the quality of your project. 

For example, if the scope of a project expands, it will most likely cost more and take more time to complete. Failing to plan for this and allot more funding will cause the project to come in over budget. Failing to increase the time constraint will most likely make the project miss its deadline.

Project managers must always balance the three factors to keep project goals aligned. When one variable changes, the others must change too, or the triangle can break and the deliverable won’t meet the expected quality standards. 

When you first hear about the triple constraint triangle, also commonly referred to as the "iron triangle", it can be intimidating. But don’t let the geometry terms deter you from understanding the model and how it can help you become a savvier project manager — there isn’t any math to worry about. 

Picture the model with each constraint making up a point of the triangle. Inside the triangle is our goal, which is quality.

This model simply represents the relationship between the time, scope, and cost constraints when managing projects. Let’s take a closer look at each of these.

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The time factor refers to the amount of time required to finish tasks within the project and the amount of time the team needs to see the project through to completion. Although timelines change, the goal is to get as close as possible to a realistic time estimate for each phase of work. 

Of course, the time your team needs to get the job done could easily change if the scope of the project, or the scope constraint, expands or contracts. The time constraint is directly related to the number and intensity of requirements that make up the scope constraint. The larger the scope, the longer the time constraint becomes. If the scope keeps changing, the time constraint needs to change, too, or the project risks going over the deadline.

The cost constraint can also affect the time constraint. They typically move in opposite directions. For example, if the cost of buying ads or paying contractors goes down, you may be able to increase the time dedicated to your project. If the budget’s cut, this might affect the number of team members working on the project. Fewer hands on deck means, you guessed it, the project takes longer to complete.

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The cost of a project or the “budget” is simply how much money you think it will take to complete the project (whether it’s a marketing campaign, product launch, internal audit, etc). This includes things like supplies and materials, labor rates, advertising fees, risk estimates, and so on. 

Before a project starts, the client receives a quote that lays out the project's cost. If the client accepts it, they expect the project to cost what the quote says it will. Project managers need to keep costs in line.

However, the cost constraint is affected by the project scope. For example, let’s say a website design company is working on a 20-page website and the client decides they want to add 10 more pages. That’s a scope change. There’s no way the design company can add those 10 pages without increasing the project’s cost.

Unlike the cost and scope, which increase or decrease together, the cost and time constraints move in opposite directions. If the budget decreases, the length of time to deliver the project generally increases. If the budget increases, then the time constraint decreases.

Scope represents the size, breadth, and depth of the end deliverable. In other words, what is your team trying to accomplish using the resources available to you? 

The project manager should write up a project scope statement outlining what the project includes and what it doesn’t before beginning. A scope statement needs to be detailed so the client or any other stakeholders understand it clearly. That way, teams can avoid the all-too-common “scope creep” that happens when individuals keep adding onto the project after agreeing on the goal deliverable. 

The scope constraint is impacted by the cost and time constraints. As we’ve covered in the previous sections, if the scope expands, the cost has to expand, plus the time it takes to deliver the project.

Everyone with a stake in the project reaps the benefits when you proactively build a triangle. Everyone understands the constraints of project management and can contribute ideas to navigate them as they pop up. 

Agreeing on the cost, time, and scope before the project starts puts the agency and client on the same page, and gives the project a better chance of executing on goals and making everyone happy.

Let’s dive a little deeper into the four valuable benefits stemming from a proper project management triangle.

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During project execution, using the triple constraint triangle as a model helps team members understand how their actions, even if they seem small, have a bearing on the project’s success. Completing tasks within the set time frame keeps labor costs in line, while quickly addressing bottlenecks. 

Learning to think with a “triangle mentality” keeps teammates agile and focused on generating high-quality work.

The project management triangle is a powerful visual of the tradeoff that ALWAYS occurs between cost, time, and scope. 

A project team that understands this also understands the “ripple effect” that occurs across all three variables if one variable changes and can respond quickly and effectively. This knowledge increases team (and client) cohesion. The triangle keeps everyone speaking the same language and helps manage expectations.

Project management software is a great way to communicate effectively with clients. In a recent survey, 1 in 4 people said project management software is their favorite way to communicate with clients. 

Even the best teams or clients can make the mistake of piling onto the original goal or making requests that seem easy but actually pushes the project out of scope. Fortunately, the triangle model directly correlates scope with the project cost and timeline. It makes it much easier to see and communicate how these changes can snowball. 

When your team can demonstrate that the more they add to the project, the longer and more expensive it becomes, these kinds of stakeholders are more likely to cool their jets on changes that weren’t in the original scope statement. 

The project management plan will always be to stay on time and within budget, but we all know things can go sideways without careful planning. 

By using the triangle to watch for roadblocks and steer clear of scope creep, as mentioned above, the project team can stick to the ideal project schedule, meet key deadlines, and reach milestones with ease. It’s also easier to coach team members on their time management so they know how to prioritize. 

(By the way, all this is more streamlined and efficient if the team uses project management software, like Teamwork! Try it for free.) 

A triple constraint triangle is a powerful tool with impressive functionality that can change project planning and execution. But it’s not perfect all the time. Every methodology faces hurdles when applied to the real world. 

Each variable within the triangle comes with specific challenges that can cause a project to teeter toward delays, risks, or failures. Project managers must be aware of these pitfalls and proactively mitigate them during all workflow stages. 

Obstacles will crop up in almost every project, but you can be ready to anticipate them. Let’s look at some common challenges of time, cost, and scope.

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Delivering a project successfully means completing it on time. Here are some situations that can slow down progress or bring it to a screeching halt.

  • External delays: External delays are also a tough-to-control issue we see. This might be a delay in getting client approvals, having access to key materials or data, or waiting on other departments’ reviews. This can halt the progress of entire teams. Stay on top of stakeholders and communicate proactively to get what you need. 

  • An overly optimistic timeline: Thinking positively is a good thing, but project managers need to be realistic about timelines. If the plan is too ambitious, it sets the project up for failure. Take stock of your team members’ capacity, any client involvement, and upcoming projects or industry changes that might impact things. 

  • Bottlenecks: Parts of a project frequently hinge on earlier parts being finished. If there’s a holdup in the early part of the project, it could block further work and throw the schedule off track. Watch for potential bottlenecks, like an over-capacity teammate being the only handling reviews, and resolve them quickly. 

  • Staffing issues: Projects don’t finish themselves! If team members quit, go on vacation, or fall ill, they may leave gaps in the project that can cause it to stall. Teammates can also get overwhelmed and worn out, especially if a project is drawn-out and tedious. Some of them may not be committed to the project deadline. Managers need to watch out for staffing issues and have a plan to address them,

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Accurately pricing a project is difficult because of the many factors that go into the cost. Some of the biggest challenges around a project’s cost are:

  • Again, too much optimism: Just like underestimating the time a project will take, project managers can understand how much it’s going to cost too. For instance, underestimating the number of people needed or the cost of software can jeopardize the project part way through. Accurate cost estimation is key to avoiding going over budget.

  • Lax management: Project managers must watch the budget closely and track expenditures. If left unmanned, little costs can creep in, the project can use more resources than the budget entailed, and the project can end up over budget. Time tracking software and other resource management tools are helpful here. 

  • Funding or resourcing delays: Whoever said “time is money” couldn’t have been more correct. Trying to clear bottlenecks, waiting on materials, and working out staffing issues can keep the project bill ticking upward ominously. Project managers should be proactive in dealing with these issues to keep the costs from compounding.

We can’t say enough about the danger of scope creep. It has derailed more well-laid projects than we know. The scope variable may face significant challenges of its own:

  • Poorly planned projects: If the project plan isn’t detailed enough with requirements, tasks, limitations, and outcomes, you’re asking for trouble. Once the project’s moving, the project team and the client may not understand what is included in the project, who is accountable for each task, and in what order the tasks should be completed. This scenario is also a perfect breeding ground for scope creep.

  • Scope change: Adding elements to the project once it’s underway is risky. These will take more resources, driving the cost up, and/or take longer to complete. If a client tries changing the scope, communicate with them and lay out the consequences (i.e., the project will take longer and be more expensive). Here’s how to provide a detailed project estimate and start off on the right foot.  

  • Internal expectation changes: Clients aren’t the only ones who may try changing the project’s scope. Other stakeholders — like higher-level directors or other departments you collaborate with — may jump into the mix and attempt to make changes. Similar to the other challenges we’ve covered, get buy-in to your plan on the front end and be ready to explain how these requests will impact your project constraints. 

“You can have it good, fast, or cheap. Pick two.“ This idea that in any set of three qualities, only two can be delivered well is a good summary of the triple constraint. Here are some examples of how you can adjust the different constraints to achieve your goals: 

  • To speed up a project (time), you could reduce features (scope), dedicate more resources (cost), or do both. 

  • To increase the size or depth of the deliverable (scope), you can add people to work faster (cost), extend the deadline (time), or do both.

  • To complete a project under budget (cost), you can cut elements (scope), reduce the number of workers or resources, and extend the amount of time it takes to finish (time).

A project manager's ability to balance time, cost, and scope within the triple constraint triangle is key. Simple as it may seem, being able to grasp and manage the three sides of this model helps you better control the outcome of every project. 

You can take your learnings from the model and share them with company stakeholders or clients to set healthy expectations from the start and revisit them as the project progresses. 

Do you need a better way to manage your project’s communications and tasks too? Teamwork offers real-time and asynchronous communication, task management, time tracking, workload monitoring, and more. Set your project on a path to success by adding Teamwork to your project management tool set.