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Managing Scope
A Project Management Triple Constraint Example & Guide

What are the three primary variables (or triple constraints) in any project?

If you’ve ever taken a project management course, you’ve probably got a knee-jerk response to this question:

  1. Scope
  2. Time
  3. Cost

For over fifty years, the Triple Constraint Theory has been the standard within project management circles. In recent times, however, there’s wider recognition of more than just three constraints.

Here, we explore both the conventional concept and new perspectives that have surfaced. We take a look at both the practice and the theory of the “Iron Triangle” project management professionals have come to know over the years. Lastly, we discuss practical methods showing how you can use the Triple Constraints to manage competing priorities in real life.

Triple constraint

Why Does The Project Management Triple Constraint Matter?

Why does the triple constraint (or any project constraint) matter? Why are we talking about it?

Keeping the three elements of the Triple Constraint in mind as you manage a project will help you adapt to changing conditions while still delivering projects on time, within budget, and within scope. Change is a given in project management, and being adequately prepared ensures that changes don’t jeopardize the entire project and the relationships involved. This is why we must understand and effectively manage the project management Triple Constraint.

What Is The Project Management Triple Constraint?

Also referred to as the “Project Management Triangle” or the “Iron Triangle”, the Triple Constraint represents the relationship between a project’s scope, time, and cost. They’re usually represented like this:

Triple constraint quality

Let’s dive into each side of the triple constraint triangle to explain this further:


Project Scope refers to the extent range, breadth, reach, confines, dimension, realm, gamut, spectrum, or spread of the work that’s to be done on a project. It encompasses the sum of all the products and services to be provided, describing what’s being done and how much of it. You can learn more about Scope of Work in our complete SoW guide.


Simply put, the amount of time you need to complete the project or tasks within the project.


Project cost refers to the resources—financial and otherwise—required for the project. It might include labor costs, hardware, software, and other charges.

How Does The Triple Constraint Work?

The Triple Constraint doesn’t exist to merely help us remember to list out our project’s scope, time, and cost. The whole premise of the Triple Constraints of project management is that the three factors of scope, time, and cost are inextricably linked.

There’s a give-and-take relationship between scope, time, and cost. Therefore, the Triple Constraint concept dictates that if you make any changes to any one side of the triangle, it will have effects on the other sides of the triangle. Takes you straight back to geometry class.

The most common model places “quality” in the center of the triangle. This is simply to illustrate that the quality of a project depends on the project’s scope, budget, and time spent on the project. The idea is that, if you are to maintain a consistent level of quality (or, in geometry class, the consistent area within the triangle), when making changes to one side of the triangle, the other sides must adjust.

All math aside, this idea is intuitive. If you’re going to ask for something to be delivered faster (time), you have to pay more (cost). If you’re trying to save some money (cost), sometimes you can do this by choosing a simpler version (scope).

The Triple Constraint is especially helpful in conversations with clients, both when initially determining the scope of a project and when handling Change Requests along the way. Digital agencies live in a competitive environment, and it’s common to feel pressure to deliver something comprehensive as cheaply as possible (and quickly!).

While that is possible in some scenarios, the Iron Triangle reminds us that most of the time, projects cannot be cheap, comprehensive, and fast all at once. We have to know our priorities in order to decide “what’s gotta give”.

Triple constraint venn diagram

A Triple Constraint Example

Let’s take an e-commerce website built with a budget of $500,000 and a timeline of 6 months.

  • Scope: E-commerce website
  • Time: 6 months
  • Cost: $500,000

Let’s use a familiar scenario. Say the client originally thought that they’d be able to supply content from their team, including SEO-friendly product descriptions. They’ve recently found out that their team doesn’t have any available cycles to produce the content, and they’ve gotten in touch to ask you about having your project team do it.  With the Iron Triangle in mind, when you get this request from the client you remember that you can’t increase the scope without factoring in its relationship with time and cost.

Naturally, the client would prefer to change the scope without the time or cost of the project changing (this is a whole issue in and of itself—see our post on managing scope creep). However, a savvy project manager understands the dynamic between scope, time, and cost—and you know that trade-offs are inevitable. To successfully manage the project, the PM must help key stakeholders understand this dynamic, too.

The Project Management Triple Constraint Is Not A Triangle Anymore

There have always been mixed opinions as to the accuracy and usefulness of the Iron Triangle. Some think that the Triple Constraint model is inaccurate and impractical. Some theories have stuck with the triangle concept but changed the types of constraints on each side. Regardless of the varying perspectives, one thing that every PM intuitively knows is that there are many more constraints to a project than just scope, time, and cost. In reality, managing a project is more complex than the Iron Triangle variables suggest.

In recognition of the limitation of the model, the Project Management Institute (PMI) has extended the number of constraints. In its latest version of the Project Management Body of Knowledge (PMBOK), the PMI does away with the project triangle in recognition of the fact that project managers usually deal with more than three project constraints. The PMBOK Guide now includes the following in their list of project constraints:

  1. Scope
  2. Quality
  3. Schedule
  4. Budget
  5. Benefit
  6. Risk

We’ve already looked at Scope, Schedule (Time), and Budget (Cost). Let’s look at the PMBOK’s additional three constraints:


The Quality constraint is similar to Scope—except that Quality focuses on the characteristics of a deliverable.


Benefits represent the value the project is expected to deliver to the organization; for example, increasing sales or improving customer service.


Risk refers to the probability that an event that affects the project will occur and its potential impact. This constraint has to do with the level of risk the project stakeholders or team are willing to tolerate.

These additional variables are legitimate project management constraints, but the simple model of the Triple Constraint is still great for conceptualizing the relationship between the high-level dynamics involved in project management.

The Project Management Triangle In Real Life

Understanding the theoretical relationship between project constraints is important. However, it doesn’t do us much good if we don’t know how to manage them in all the grittiness and grey areas of real life.

The following section summarizes some best practice info for applying the Triple Constraint model to projects in real life.

Best Practice For Effectively Managing The Triple Constraints

Although admittedly simplistic, the project management Triangle is often a useful way to represent expectations in a project. Here’s how to use it in real life to figure out your clients’ priorities and, in turn, establish parameters that make the most sense.

Deciding on priorities is only the first step. Moving forward, you have to ensure you’re monitoring the right metrics so you can keep tabs on your scope, time, and cost.  I’ve included some useful tools in the sections below.  Additionally, you can scan our list of the best project management tools, most of which include a bundle of features for tracking time, scheduling resources, and creating process documentation.

Is Cost The Biggest Priority?

If you absolutely have to stay within a fixed budget, then the client may need to be more flexible on time frame and scope. With cost as the biggest priority, it’s likely that only the most business-critical change requests will be approved.

So, when changes come up, you’ll probably look to these measures:

  • adjust the project deadlines
  • scale back the scope of the project
  • agree upon reduced quality of certain project deliverables

To help you communicate the costs and cost estimates of the project to your clients, use resource management software, where you can draw up reports on your team’s capacity, resource utilization, and performance for projects, clients, and individuals.

You’ll also want to use a Gantt chart to create a detailed work breakdown structure—here’s a review of project management software for creating Gantt Charts.

Is Time The Biggest Priority?

In cases where the deadline matters most, then more flexibility will be required with respect to the cost and/or scope.

Expediting the project to satisfy the time constraint might mean:

  • putting more resources on the line, increasing cost
  • cutting back the scope and/or quality of the end product

Especially when precise time estimates and deadlines are a priority, you should take a moment to set yourself up with the right time-tracking tools: use past project reports to make accurate time estimates and track team hours to make sure you’re staying on schedule.

Is Scope The Biggest Priority?

If scope matters most, it might be important for the client to be able to add features throughout the project as they discover more about their customers. If what matters most is having exactly the features that they put in scope, then they have to remain open to:

  • flexible timing as the team accommodates scope changes
  • increased cost for deliverables added to the scope

No matter your project, you need a detailed, specific Statement of Work document that defines overarching project information as well as details on deliverables, standards, criteria, and requirements for each phase. Here’s a complete guide to creating a Scope of Work.


However simple, the Iron Triangle is still a valuable tool for thinking about project priorities and trade-offs between those priorities on a high level.

Project constraints will always exist. You can prepare to deal with constraints by weighing changes against the impacts on other parts of the Iron Triangle. In turn, it’s up to you as the project manager to communicate this give-and-take relationship with your clients so they understand: if one constraint changes, the other constraints are likely to be affected.

What Do You Think?

Is the model worth keeping around or should it be consigned to history in favor of more modern tools for prioritization and decision making? If so, which ones would you suggest?

By Ben Aston

I’m Ben Aston, a digital project manager and founder of I've been in the industry for more than 15 years working in the UK at London’s top digital agencies including Dare, Wunderman, Lowe and DDB. I’ve delivered everything from film to CMS', games to advertising and eCRM to eCommerce sites. I’ve been fortunate enough to work across a wide range of great clients; automotive brands including Land Rover, Volkswagen and Honda; Utility brands including BT, British Gas and Exxon, FMCG brands such as Unilever, and consumer electronics brands including Sony.

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    I think this model is great and definitely worth keeping as the quality, benefit and risk are quite similar to a project's scope. Thanks for sharing, Ben. This article was quite insightful.


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    You can only change the pyramidal triangle if you have speed and skill


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    nice read


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    Great article!! Thanks so much. This really lays out a comprehensive overview of considerations when building and responding to request for adjusting scope. The other linked articles are also extremely helpful - great layout for diverse learners (ie: including all the software logos/images, then detailed breakdowns). Thank you!


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    I believe the below constraints are still very valid. PM's sometimes get a good idea where the trade offs can be done (what is flexible, cost or time) during the charter phase and can steer the team accordingly based on what is truly important in terms of business outcomes.