Building estimators assess the likely cost of construction, renovation and repair work. They use project drawings, specifications and site information to calculate the quantities of materials, labour and equipment required, then prepare cost estimates and supporting breakdowns. Their work can cover individual trades or whole projects, from small domestic alterations to commercial and larger building schemes. Depending on the project, services may include measuring work from plans, obtaining and comparing supplier or subcontractor quotations, preparing bills of quantities and tender documents, and advising on budgets before work begins. During a project, estimators may help track spending, assess the cost of design changes and variations, and update forecasts when prices or requirements change. They typically work with clients, architects, engineers, builders and quantity surveyors; the precise scope depends on the contract and the stage of the project.