tripleconstraint

The triple constraint, also known as the project management triangle, is a model that identifies three primary constraints that define the feasibility of a project: scope, schedule (time), and budget (cost). In some interpretations, quality is regarded as a central factor that must be preserved while negotiating the other constraints, making it a broader model sometimes described as four elements. The core idea is that these constraints are interrelated and changes to one affect the others.

The three constraints are interdependent. Increasing the scope generally requires more time and higher cost, while shortening the schedule may necessitate additional resources or a reduced scope. Similarly, increasing the budget can enable faster delivery or more features, potentially impacting scope or quality if not managed carefully. The model is used to communicate expectations, establish baselines, and evaluate trade-offs during planning, execution, and monitoring.

Origins of the concept trace to mid-20th century project management discourse and it remains a common framework in professional practice, including in widely referenced guides such as the PMBOK. It supports decision-making, risk assessment, and stakeholder negotiations by making visible the relationships among what is to be delivered, by when, and at what cost.

Limitations of the model include its simplification of complex projects and its potential to encourage rigid compromises rather than value-driven outcomes. Critics note that focusing solely on time, cost, and scope can overlook quality, risk, and strategic alignment. Modern practice often treats the triangle as a starting point for broader considerations of value, benefits realization, and stakeholder expectations.