Cone of Uncertainty

Describes the evolution of uncertainty as a project or task moves forward


In the beginning of a complex project, it is very difficult to estimate the level of effort it will take to complete it.

At this point in the project there are many unknowns that will influence the amount of work needed to complete the project.

As the project progresses, the uncertainties become known, and therefore, more predictable, making it easier to estimate.


Break the complex project into smaller projects.

For example, break the complex project into two:

  1. The known part of the project
  2. The unknown part of the project

Then estimate the known part of the project.

It is likely that by the end of the known part of the project, the unknown part of the project will become apparent.