Software cost estimation has been growing in importance till today. This is not a surprising fact that various difficulties are observed when estimating software costs. The major amount of the total costs of a project arises from the salaries of the personnel. Other costs, as license fees or new equipment for example, occur only once and are not too hard to estimate. Its a difficult task to measure software cost. These are various methods which were evolved time to time for cost estimation. A lots of examples of are given for cost estimation by different methods like Delphi, Analogy, COCOMO II etc.