This work proposes a metric to assess the spread of the switching frequency profile of power converters, focusing on Finite Control Set-Model-Predictive-Control (FCS-MPC)-based converters, and analyses the effect of the filter sizing, sampling period, and cost function on the switching frequency spread. An algorithm that estimates the instantaneous switching frequency is the basis of the proposed metric. The literature review shows that only two metrics, THD and average switching frequency, are used to assess the switching frequency of FCS-MPC, but the findings of this research show that both are insufficient to characterize FCS-MPC. The main contribution of this paper is that now researchers can quantitatively assess the switching frequency spread of FCS-MPC through the proposed metric.