Cost Plus Estimate is a type of cost estimating method that adds a specific percentage of estimated costs to the supplier’s actual costs. This approach works well when you need a ballpark figure for your project, but it doesn’t provide any assurance of accuracy. It’s important to understand that the margin of error can be quite large depending on the assumptions and calculations used to create the estimate. Also, because it’s based on an assumed percentage rate, it can be difficult to assess what it actually covers and how reliable it is. Cost Plus Estimating is best used in cases where you are working with a trusted vendor who has experience in similar projects and can provide reliable cost estimates.