The 100% Rule

Project Planning: The 100% Rule for a Product Breakdown Structure

The Product Breakdown Structure (PBS) provides a visual representation of the physical components of a product, project, or system, under consideration. By providing a representation of project outputs in the form of a diagram, PBS allows its users to obtain a clear understanding of the projects requirements. One vital principle that guides the development, decomposition, and evaluation of the PBS is the 100% Rule.

product breakdown structure 100% Rule

As can be seen in the PBS above, the top level of the PBS diagram is essentially an overview of all project requirements. The product breakdown structure then "breaks down" the project into more detailed components.

An accurate definition of each project component is a key to organized project management. The 100% Rule ensures that this accurate defining takes place. When a PBS is developed for a new project, it must encompass all physical requirements of that project. It is in this way that adopting the 100% Rule reassures managers that all elements of a project are accounted for and that nothing goes without consideration.


Application of the 100% Rule and the PBS enable all outcomes to be considered in order to ensure an accurate projection of a project outcome. Furthermore, all elements of a project are likely to be considered when the 100% Rule is applied. When the 100% Rule is applied, project planners can provide a visual diagram that contains a thorough representation of a project and its outcomes.

The PBS is the launching point in the planning process, as planned outcomes must be defined before components of a project can be considered. If outcomes are not accurately defined during this primary phase, the project is destined to fail. Incorporating the 100% Rule provides a detailed understanding of all necessary outcomes of a project. This explains why the 100% Rule is a vital principle for an accurate PBS.