In 20 years, from 1996 to 2016, global cumulative container port throughput had an average annual growth rate of 6.3%. Furthermore, the average global transshipment incidence increased from 11% in 1980 to a stable 27% in 2017. This change in transshipment market dynamics has led to opportunities for potential port investments or disinvestments. In this research, a tool is developed for Royal HaskoningDHV that improves transshipment forecasts. The developed tool calculates the optimal ports for transshipment, transshipment throughput volumes, fleet utilization, and optimal cost routes. This is done by means of minimizing the total transport costs, while meeting container demand requirements and port and vessel constraints. The most statistically significant factors affecting transshipment volumes are incorporated in the tool. By modifying input parameters, the tool facilitates calculations of optimal cost future transshipment port throughput volumes. This could provide key insights in lucrative port investment or disinvestment opportunities.