Bottom-Up Cost Estimating

Bottom-up estimating is a method where the cost of individual work packages or activities is estimated at the most detailed level and then summarized or rolled up to determine the total project cost. The cost and accuracy of bottom-up estimating are typically driven by the size and complexity of the individual work packages or activities.

This technique generally requires the project scope to be well defined and decomposed to a granular level through the work breakdown structure (WBS). Because it estimates each piece of work individually, it tends to produce the most accurate results but is also the most time-consuming and expensive estimating technique.

Bottom-up estimating is often used when a detailed and accurate estimate is needed, such as during detailed planning or when a fixed-price contract requires precise cost figures.