The progress (percent complete) is calculated by using a weighted average method of computing "earned" hours or work units. Estimated hours or work units are allocated to all physical items of project deliverables, tasks or activities (drawings, specifications, documents for engineering; interim milestones for procurement; foundations, pipe spools, instrument tags, etc. for construction). This assignment of hours or units provides a "weighting" relative to the respective disciplines control budget. A "percent complete" is then applied to each item yielding the earned hours as shown: