The Project Triangle: Viewing Projects in Terms of Time, Cost, and Scope

You can visualize project work in many ways, but our favorite method is what is sometimes called the project triangle or triangle of triple constraints.

This theme has many variations, but the basic concept is that every project has some element of a time constraint, has some type of budget, and requires some amount of work to complete. (In other words, it has a defined scope.) The term constraint has a specific meaning in Project, but here we’re using the more general meaning of a limiting factor. Let’s consider these constraints one at a time.

Time

Have you ever worked on a project that had a deadline? (Maybe we should ask whether you’ve ever worked on a project that did not have a deadline.) Limited time is the one constraint of any project with which we are all probably most familiar. If you’re working on a project right now, ask your team members to name the date of the project deadline. They might not know the project budget or the scope of work in great detail, but chances are they all know the project deadline.

The following are examples of time constraints:

• You are building a house and must finish the roof before the rainy season arrives.

• You are assembling a large display booth for a trade show that starts in two months.

• You are developing a new inventory-tracking system that must be tested and running by the start of the next fiscal year.

Since we were children, we have been trained to understand time. We carry wristwatches, paper and electronic organizers, and other tools to help us manage time. For many projects that create a product or event, time is the most important constraint to manage.

Cost

You might think of cost simply in monetary terms, but project cost has a broader meaning: costs include all of the resources required to carry out the project. Costs include the people and equipment who do the work, the materials they use, and all of the other events and issues that require money or someone’s attention in a project.

The following are examples of cost constraints:

• You have signed a fixed-price contract to deliver an inventory-tracking software system to a client. If your costs exceed the agreed-upon price, your customer might be sympathetic but probably won’t be willing to renegotiate the contract.

• The president of your organization has directed you to carry out a customer research project using only the staff and equipment in your department.

• You have received a $5,000 grant to create a public art installation. You have no other funds.

For virtually all projects, cost is ultimately a limiting constraint; few projects could go over budget without eventually requiring corrective action.

Scope

You should consider two aspects of scope: product scope and project scope. Every successful project produces a unique product: a tangible item or service. Customers usually have some expectations about the features and functions of products they consider purchasing. Product scope describes the intended quality, features, and functions of the product-often in minute detail. Documents that outline this information are sometimes called product specifications. A service or event usually has some expected features as well. We all have expectations about what we’ll do or see at a party, concert, or sporting event.

Project scope, on the other hand, describes the work required to deliver a product or service with the intended product scope. Project scope is usually measured in tasks and phases.

The following are examples of scope constraints:

• Your organization won a contract to develop an automotive product that has exact requirements-for example, physical dimensions measured to 0.01 mm. This is a product scope constraint that will influence project scope plans.

• You are constructing a building on a lot that has a height restriction of 50 feet.

• You can use only internal services to develop part of your product, and those services follow a product development methodology that is different from what you had planned.

Product scope and project scope are closely related. The project manager who manages project scope well must also understand product scope or must know how to communicate with those who do.