For effort estimation, among various inputs, size is the most vital one. The estimation of effort and cost depends on the accurate prediction of the size. Given the central role that software size plays in the Software Cost Estimation, software developers are increasingly focusing on process improvement in the software size estimation area. This demand has spurred the provision of a number of new and /or improved approaches to software size estimation. Among all, Object-oriented technology is becoming popular in today's software development environment. There are various methods available for establishing the relationship between the size estimation metric and effort. This paper aims to establish statistics relation using mathematical approach. Statistical correlation is being calculated between the two variables to measure the dependability of the relationship and determining the precision of a relationship

The accuracy of an estimate is always questionable. Lots of efforts have been put to make an estimate more accurate. In case of a software project, the accuracy of estimate is dependent on the correctness of size estimation. Size is a critical factor in determining cost, schedule, and effort. Poor size estimation may lead to budget overruns and late deliveries, which decreases the confidence of customer and erodes the image of developer. Traditional size estimation methods generally used are source lines-of-code, function point, object points etc. However, traditional size metrics have limitations and are not compatible with newer rapid prototyping and object-oriented approaches of software development. This paper critically analyzes the lacunas of traditional methods and introduces Object oriented metrics for effective size estimation for Object Oriented Software.