A estimating capability of software effort, duration and cost is based on accurate size estimate of the software to be developed. A simplified function point (FP) approach to software size estimation is described, which first skip the computation step for value adjustment factor, thus directly obtaining final adjusted FP from unadjusted FP. The research seeks suitable models based on statistical regression models in the context of case study based on 783 software projects. The approach also are built for subsets of projects using new development, enhancement and re-development types.