Computational fire spread models are a useful tool to mitigate the impact of forest fires. Simulators implementing forest fire spread models require several input parameters to deliver their predictions. Wind speed and direction are sensitive parameters that are usually obtained at low resolution (some kilometers). It is necessary to couple a wind field model, that generates a wind field at high resolution (for example, 30 meters). Even in this case of coupled wind field model-forest fire spread simulator, several parameters include a high degree of uncertainty and usually must be calibrated. One of the strategies consists to introduce a Genetic Algorithm (GA) to calibrate the input parameters according to the actual evolution of the fire. GAs are based on running large amount of simulations, and evaluating and comparing the results provided by each simulation. This fact emphasizes how critical are the metrics used to assess the error of the computational forecasts. The goal of this work is to test eight functions to assess the simulation errors in the case of coupled wind field-forest fire spread prediction to study their drawbacks and advantages to determine which is the most relevant error function.