(Accuracy -25, +75 Percent) This is an approximate estimate made without detailed data, that is usually produced from cost capacity curves, scale up or down factors that are appropriately escalated and approximate cost capacity ratios. This type of estimate is used during the formative stages of an expenditure program for initial evaluation of the project. Other terms commonly used to identify an Order of Magnitude estimate are preliminary, conceptual, factored, quickie, feasibility and SWAG.
(Wideman Comparative Glossary of Common Project Management Terms v2.1Â )