preestimate

A preestimate is an initial, rough estimate of the size, cost, time, or other quantity associated with a project, task, or decision, produced early in the process before detailed analysis or complete information is available. It is used to assess feasibility, set expectations, and inform early planning and approvals. A preestimate is typically provisional and accompanied by explicit assumptions and an uncertainty range.

In practice, preestimates are common in project management, construction, software development, product planning, and budgeting. They rely on limited data, high-level requirements, historical experience, rules of thumb, or expert judgment rather than full scope definitions or detailed quantities. A preestimate is distinct from a detailed estimate or a formal budgeting exercise, which use complete specifications, unit costs, and risk analyses. To communicate reliability, preestimates often present a wide interval or a confidence band.

Methods for forming a preestimate include analogous estimation (using data from similar past projects), parametric estimation (cost per unit times estimated units), top-down budgeting, and quick vendor quotes. The estimate should document key assumptions, method, and data sources, and should be updated as new information becomes available. Common risks with preestimates include optimistic bias and underestimation of scope changes; therefore, they should be treated as provisional and revised during later planning stages.

See also:

- estimation

- preliminary estimate

- rough order of magnitude

- ballpark figure

- a priori estimate

Example: an early proposal might state a preestimate of 6–9 months and $500,000–$800,000 for a software project, based on similar prior work, before detailed requirements are known.