One of the most contested and controversial issues that often arises in construction claims is the calculation and/or estimation of lost productivity on a construction project. Contractors prefer to use estimation methods while owners often insist on using actual cost data, which in many cases does not exist. Tracking efficiencies and productivity on any project is often overlooked, but it can greatly affect the value of a loss of productivity claim if done correctly or incorrectly when pursuing a change orders or claims. This article will present the common pitfalls of typical loss of productivity claims based on measured mile analyses and industry studies, as well as, lessons learned and observations from actual construction claims. The article will also examine the pitfalls, why they occur, and how to avoid them in preparing a claim.