Estimation is the important first step to plan development of any software application. Size, effort, timelines and cost are the key parameters that need to be estimated. These parameters act as input to the overall project plan. Out of these parameters only size is the independent parameters while others parameters depend on size. There are two type of Software sizing one is based on functional size (user perspective) and other is technical size (developer perspective e.g. KLOC) but technical sizing cannot be used to compare functionality provided by software application.