This paper presents a tool to simulate the biomass production capacity of microalgae-based processes as a function of the prevailing weather conditions at selected locations around the world. The tool is designed for the use of raceway reactors operated in turbidostat mode, allowing for the simulation of biomass production at whatever location for different strains as a function of reactor size, culture depth, and biomass concentration in the reactor. The tool integrates the solar radiation and temperature data available in existing databases for the selected location to determine the light availability and temperature impact in the culture, to finally provide the growth rate and biomass productivity. Hourly values are calculated to estimate a detailed overview of cultures performance, and finally, mean daily and annual values are calculated. The simulation tool developed is a very useful instrument for decision-making processes about the installation of microalgae-related facilities, and also allows the determination of the potential production capacity.