The Certified Lean Project Manager® triangle of constraints

The traditional iron triangle of constraints identifies three main types of constraints on the success of a project: scope, cost, and schedule. Change to any one of these constraints will affect the others. A project’s quality depends on satisfying all three constraints.

The Certified Lean Project Manager® triangle reverses the traditional triangle of constraints

Scope
Scope is the primary constraint because it’s the first constraint that’s known. Scope determines the project’s size and is defined by the components a product should contain. The cost and schedule constraints can be adjusted to accommodate a change in scope.
If a customer requests additional features, the project scope increases. You may need a larger budget, more time, or both to allow for this. There may be some details that indicate which components are more important than others, should time or money run out.

Cost
The constraint of cost refers to the limits posed by a project’s budget. The budget contains a list of planned expenditure and revenue for the project. If costs are higher than planned, the scope or schedule may need to be adjusted.
For example, a budget overrun may make it necessary to reduce product features. Or it may mean extra time will have to be added to the schedule because fewer resources will be available for completing the required work.

Schedule
The schedule constraint refers to the time limits posed by project deadlines, including interim milestones and a final release date. The schedule refers to the timeline or the main delivery dates.

If a customer requires that you deliver a product earlier than planned, for example, costs may increase because you need to hire more staff. Alternatively, you may have to decrease the project’s scope.

The agile approach rejects the traditional iron triangle because the traditional version measures success in terms of how well a project conforms to defined plans, instead of in terms of value to customers and the development of working software. What’s known as the agile iron triangle reverses the traditional triangle, recognizing the importance of meeting a fixed, or time-boxed, schedule as the main constraint. Cost and scope are the variables.
Using this triangle, a project’s success is still measured in terms of how well a project meets a predetermined scope, cost, and schedule. As such, it still fails to recognize the value of a project’s ability to change. The lean project management triangle measures a project’s success in terms of its ability to respond to change, or meet its main goal of delivering value to the customer. Other goals are to deliver quality while working within certain constraints.

Value
Value is the main goal because a project’s success is measured by how much value it brings to the customer. The better you can adapt to and meet changing customer requirements, the more value you bring to the customer. To achieve this goal, it’s possible to adjust quality and various constraints.

Quality
In lean project management, you achieve the goal of quality by continuously delivering value to customers through workable products. Quality is a non-negotiable condition of satisfaction. In lean project management, value and quality are built into every step of the process. If there are any specific conditions of satisfaction to confirm quality, they vary depending on the type of project and what’s being developed.

Constraints
A project’s constraints are its scope, cost, and schedule.

You adjust the constraints so you can meet the main goal of delivering value and quality to a customer. The schedule is often a fixed constraint but you can vary scope to remain within acceptable costs. When adjusting scope, you should focus on whether you can release a workable product, as opposed to how many features the product has on release. Delivering workable software with fewer features creates more value for a customer than delaying delivery so you can incorporate all features.

Learn how to use Continuous improvement and build a culture of stopping to fix problems, to get quality right from the first. Enroll in the Certified Lean Project Manager®