Porosities of several metal-organic frameworks (MOFs) are computationally analyzed and discussed regarding their sensitivity to numerical parameters. Further, we investigate and discuss the influence of the probe radius on the calculated porosities. A clear differentiation between void and accessible porosity is carried out. This is essential as it impacts the comparison to experimental and theoretical results. We present two different approaches to calculate porosities, and discuss their advantages and drawbacks. All results are compared to well established methods. It will be highlighted that the calculated properties are numerically sensitive to the choice of the used approach and numerical parameters.