One of the central problems in software engineering is the inherent complexity. Since software is the result of human creative activity and cognitive informatics plays an important role in understanding its fundamental characteristics. This paper models one of the fundamental characteristics of software complexity by examining the cognitive weights of basic software control structures. Cognitive weights are the degree of the difficulty or relative time and effort required for comprehending a given piece of software, which satisfy the definition of complexity. Based on this approach a new concept of New Weighted Method Complexity (NWMC) of software is developed. Twenty programs are distributed among 5 PG students and development time is noted of all of them and mean is considered as the actual time needed time to develop the programs and Understandability (UA) is also measured of all the programs means how much time needed to understand the code. This paper considers Jingqiu Shao et al Cognitive Functional Size (CFS) of software for study. In order to validate the new complexity metrics we have calculated the correlation between proposed metric and CFS with respect to actual development time and performed analysis of NWMC with CFS with Mean Relative Error (MRE) and Standard Deviation (Std.). Finally, the authors found that the accuracy to estimate the development time with proposed measure is far better than CFS.