The effort estimation in early stages of the life cycle of software projects is an essential tool for making business decisions at the need for a methodology together with an estimation model is the key to start or abort development projects software. This paper presents a new methodology to determine the economic viability of a software development project, which is called WEM (Web Estimation Methodology). The methodology consists of a series of steps that must be performed early in any software development process. WEM includes a parametric model estimation of effort, the effort is calculated by estimating the amount of man-hours needed to meet with a set of functional requirements of a system. Parametric estimation model receives as input the size of the software on a new metric called Web Points, then by definition of time constraints, budget constraints, expected returns and effort, determines whether the project is feasible within the technical and financial expectations of the company. The methodology has been successfully tested in various development projects executed by the company Expert Information SA.