What accuracy range can typically be expected from Order of Magnitude Estimates?

Order of Magnitude Estimates are typically used in the early phases of project development when there is limited project detail available. They are intended to provide a rough estimate of the potential costs and can vary significantly based on the assumptions made, the level of information available, and the uncertainty inherent at this stage.

The accuracy range of +50 percent or -30 percent is aligned with the purpose of Order of Magnitude Estimates. This wide range reflects the significant variability that can occur when estimating costs with minimal data available. It is crucial for stakeholders to understand that, while these estimates can provide a general idea of costs, they carry a substantial risk of inaccuracy due to the lack of detailed information and analysis at this early stage of project planning.

In contrast, the other accuracy ranges presented would suggest a level of precision that is typically not achievable without more detailed information about the project, which usually becomes available at later stages, such as in Preliminary or Detailed Estimates. Therefore, the chosen accuracy range for Order of Magnitude Estimates correctly captures the inherent uncertainty of initial cost forecasting.