This paper analyzes the existing types of duration estimation models for software projects and advances a new, user-friendly model for project duration estimation. The Metrix model is a stochastic model for software project duration estimation using Monte Carlo simulation over an activity graph. The first advantage of using the Metrix model is that it produces a probability distribution of the software project duration and not a single estimate for duration. Further to this approach, we diminish the project uncertainty by giving the manager better control over the project duration and the associated probability of a certain duration outcome. The second advantage of the Metrix model is that for Monte Carlo simulation it relies upon the historic duration estimation of the team members and not on probability distribution functions which are rather difficult to come with. JEL classification: L86 computer software, O22 project analysis.