Interior designers have the expertise to evaluate the scope of a project and estimate its time and cost by devising a comprehensive plan that outlines the tasks and milestones involved. They can also obtain quotes from vendors and contractors for the necessary materials and labor. They consider several factors, including the size, complexity, and location of the project.

Additionally, they include other expenses like permits, transportation, and unforeseen costs into their calculations. Based on their experience in the industry and established principles, they can anticipate the project's timelines. These projections are then updated based on feedback and design changes provided by the client. They closely monitor the project's progress and adjust the budget and timeline as necessary.