Estimates can be prepared at any stage during a project but in order to make use of an estimate it is important to consider its purpose, the stage of the project when it was prepared and the degree of risk in the project. To have any meaning, the purpose of any estimate must be linked to the stages of the project and to the data available. Engineers have become all too familiar with the sequence of unrealistic estimates which are produced and then superseded during the life of a project. In many cases there is insufficient investigation of the reason for the poor quality of the estimate and consequently estimates have not always been treated seriously. Project cost estimating offers practical advice and further information on the understanding, the preparation and the use of estimates in the civil engineering industry. The guide is split into two parts: the first dealing with estimating at different stages of construction projects, and the second with the practice of estimating, in terms of the human characteristics of the estimator and the use of computer based systems.