{"id":732,"date":"2020-04-21T11:42:26","date_gmt":"2020-04-21T11:42:26","guid":{"rendered":"http:\/\/project-management.info\/?p=732"},"modified":"2023-08-19T07:07:35","modified_gmt":"2023-08-19T07:07:35","slug":"definitive-estimate-vs-rom","status":"publish","type":"post","link":"https:\/\/project-management.info\/definitive-estimate-vs-rom\/","title":{"rendered":"Definitive Estimate vs. ROM\/Rough Order of Magnitude (+ Calculator)"},"content":{"rendered":"\n
When the cost of projects (or parts of a project) is estimated, the accuracy of these estimates depends on various factors. These include but are not limited to the availability and quality of information and the estimation technique used. The available options and data to estimate costs typically vary among the phases of a project.<\/p>\n\n\n\n
Definitive estimate and rough order of magnitude (ROM) are two classes of estimates that are defined in PMI\u2019s Project Management Body of Knowledge. They differ in their levels of accuracy. ROM normally has an accuracy range between -25% and +75%. For definitive estimates, it ranges from -5% to +10% (PMBOK\u00ae, 6th<\/sup> ed., ch. 7.2).<\/strong><\/p>\n\n\n\n Read on to learn more about the types of estimates and use the calculator embedded in this article to quantify the ranges of your project.<\/p>\n\n\n In project management, there is a terminology for the classification of cost estimates by their accuracy. When communicating estimated costs (or durations), indicating the type of estimates provides important background on the accuracy of the estimates.<\/p>\n\n\n\n Common terms include:<\/p>\n\n\n\n The types marked with an asterisk (*) are in accordance with the current PMI framework. Unfortunately, the use of these terms and the underlying ranges vary significantly across industries and organizations. Some organizations use their own frameworks with internally predefined ranges of such accuracy classifications. Read on for some examples of such types and accuracy ranges.<\/p>\n\n\n\nTypes and Accuracy Classes of Estimates<\/h2>\n\n\n\n