The concept of capacity associated to service level is something that can be used with simulation in several situations that involve logistic and commercial planning of organizations, because it enables a practical vision of real behavior of a system, facilitating the comprehension of existent bottlenecks. This paper presents a methodology of determination of capacity of a port from offered service levels, using a discrete events simulation model developed in software ARENA. Moreover, it is considered the systemic approach as methodology, enabling a more practical and fast determination of operational bottleneck. The simulation model can to reflect strategies that would be implemented to boost the current port's capacity and demonstrates that it would increase capacity from 39.5 to 64.2 Mt/year, with the berths being the only resources that would achieve the 85% utilization threshold.