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Project management triangle

The triple constraint theory in project management

Reading time: about 8 min

Project managers know that projects never go exactly as planned. There is always something that will put the project at risk. Maybe it goes over budget, or stakeholders unexpectedly add more features to the scope, or you fail to deliver it on time. 

You could throw more money at it, extend the deadline, or add more developers to code new features. But that isn’t a practical solution even if your company has unlimited budgets, time, and resources. It might seem counterintuitive, but your projects need constraints. 

What is the triple constraint theory?

Any limitation or restriction placed on a project is a constraint. For example, when you set a deadline for the project to be completed and released, you have given the project a time constraint.

The triple constraint theory says that every project will include three constraints: budget/cost, time, and scope. And these constraints are tied to each other. 

Any change made to one of the triple constraints will have an effect on the other two. For example, If you move your project’s due date out by a week or two, your budget and scope constraints could be impacted in any number of ways, including:

  • The temptation to add features currently on the back burner to the project because you “have more time” (scope creep). 
  • Bringing in people from other teams to help on the project could increase the budget.
  • People from your team could be reassigned if they are not directly involved with the areas that needed the extra time. It could be difficult to get them back if they are too deeply involved in another project.

A brief history of triple constraint

The triple constraint theory (also known as the project management triangle, project triangle, and iron triangle) is nothing new. Project managers have been using it for at least 50 years. It’s possible that it came out of the Theory of Constraints (TOC) first developed by Israeli businessman Eliyahu M. Goldratt. 

The idea behind TOC is that there will always be at least one constraint in any system that can potentially put the project at risk. 

The idea behind the triple constraints of project management is that the success or failure of every project is tied to its budget, schedule, and scope. Your job as a project manager is to find a balance among the three constraints to keep your project on track.

What is the project management triangle?

The project management triangle is a model used to visualize the triple constraint theory. Let’s take a look at each point on the triangle.

Scope: This is a definition of the work that needs to be done. It documents the features and functions that will be included in this iteration of the product. The scope documentation should make it clear to everybody what will or won’t be included in the final product. You might consider using a work breakdown structure (WBS) chart to break down the scope into actionable tasks.

Time: Determine how much time it will take to complete the tasks in the scope and set a timeline for each task in each iteration. Based on the timelines, set a deadline for the final release of the product. Make sure that the timelines are realistic, especially if time is the least flexible constraint in your project. A PERT chart can help you to map out the time required for each task.

Budget/Cost: Review previous, similar projects to help you estimate how much your budget will cost. Look at the following costs to help you determine the overall budget:

  • Resources: How much will it cost to pay people working on the project? Base the costs on the estimated hours it takes to complete the tasks.
  • Materials: If you are in manufacturing, you have to consider the costs of raw materials and the supply chain.
  • Equipment: Will this project require new hardware or software? Consider the costs of upgrading vs. working with existing equipment.

Why is the triple constraint theory important for project success? 

The triple constraint theory helps you to recognize competing demands in every project. For every project, you need to decide which demand is the most important. Knowing which one is the most important makes it easier for you to make adjustments to the other two to balance the project and keep it on track. 

For example, if time is the most important and the deadline can’t be moved, you’ll need to adjust scope and budget to ensure that the project is completed by the deadline. 

Every stakeholder has their own idea about what is most important to the project. The triple constraint theory gives everybody involved a better understanding of the give and take relationship among each constraint on the triangle. This makes it easier for you and your team to adjust and adapt to changes when they come up.

How does the triple constraint work?

Triple constraint theory is not very difficult to implement. It basically comes down to learning how to effectively manage the tradeoffs among the three constraints on the project management triangle. 

The triangle itself is a visual reminder that the decisions you make to any of the constraints will have an impact on the others. You know that you always will need to manage the budget, schedule, and scope of every project you work on. But you can’t manage each of these in isolation because every decision you make has an effect on everything else.

Following are a few steps that can help you to successfully make the triple constraint theory work for you.

Step 1: Work with the client

Whether internal or external, you need to know what your client wants and expects from the project. Find out if they have a budget, scope, and timeline in mind. 

If you can’t settle on the guidelines for the project, use triple constraint to weigh options and discuss potential tradeoffs. Even though you know that adjustments might need to be made along the way, it’s still important to begin with an achievable and fair target.

Step 2: Clearly communicate the project scope

For your project to be successful, everybody involved needs to know what the scope is and what their roles and responsibilities are. They need to understand each individual element of the plan and the expected results. 

The scope helps everybody involved agree on what is being delivered. Whether clients or team members want to make a change, they need to understand the impact it will have on the triangle. Also, any changes need to be included in the project’s official documents to ensure everybody knows what’s going on.

Step 3: Set deadlines

It’s important to keep the project on track and on time. Create a timeline that is easy to read and shared in a highly visible area where team members can refer to it as needed. Lucidspark has a large library of templates, such as Gantt charts and calendars. These templates can help you create visual timelines that can be accessed from anywhere at any time and displayed prominently as a visual reference. 

Step 4: Allocate resources

You need to allocate resources efficiently. Assign the people with the right skillset to the right tasks. Making the correct assignments and ensuring that all teams have the funding and equipment they need sets you up for success.

Step 5: Monitor the project and make tradeoffs and adjustments as needed

It’s important to have a well-defined plan for any project. But if you don’t monitor the progress, the plan doesn’t do you much good. Monitoring lets you make minor adjustments while keeping the triple constraints balanced. Triple constraints theory lets you make adjustments and keep goals realistic and achievable. 

Whenever you make a change to one of the three constraints, you’ll need to compensate in one or both of the other two. Communicate any adjustments immediately with team members to ensure that everybody is heading in the right direction.

Best practices for managing triple constraints theory

Keep the following tips in mind when managing triple constraints.

  • Stick to the plan: Once you and your client have agreed on the guidelines, stick with the triple constraint structure to keep your project from going off the rails. Don’t use the project management triangle as a crutch to make frequent adjustments.
  • Know your priorities: Decide which constraints are the most important. This will help you to make better decisions that will keep your project constraints balanced.
  • Add constraints if needed: Modern implementations of triple constraint often include additional constraints such as the quality or the project and potential risks that can come up.
  • Consult with team members and stakeholders: Before you make any adjustments to the triple constraint model, talk to other people who are involved or have a stake in the project. Opinions from a different perspective or viewpoint can help you find the right balance among all factors. Department heads and executives can be helpful when determining how changes might affect their teams and what might need to be altered to offset the changes.
Project management triangle

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