In this study, the air permeability of electrospun polyacrylonitrile nanofibrous webs was investigated using an experimental and numerical approach. The effects of four processing parameters, including solution concentration, applied voltage, feed rate, and collector speed, were studied using a Taguchi L9 orthogonal array. Scanning electron microscopy images showed that the produced webs had a continuous, porous, and bead-free structure. The experimental results indicated that changing the electrospinning conditions simultaneously affected the structural characteristics of the webs; the mean fiber diameter ranged from 194 to 563 nm, the web thickness from 3.50 to 23.67 µm, and the porosity from 71 to 97%. The air permeability of the samples varied from 4.09 to 89.17 mL cm⁻² s⁻¹. The highest permeability was obtained for sample 4, with a web thickness of 3.50 µm and a fiber diameter of 293 nm, whereas the lowest permeability was observed for sample 7, with a fiber diameter of 563 nm, a thickness of 16.00 µm, and a porosity of 81%. These results showed that the permeability of nanofibrous webs cannot be interpreted using a single variable such as fiber diameter or porosity alone; rather, it is governed by the combined effects of fiber diameter, web thickness, porosity, and the connectivity of flow paths. To numerically predict permeability, the three-dimensional web structure was reconstructed in MATLAB based on parameters extracted from SEM images. After meshing in Avizo software, airflow was simulated through the web thickness direction. Comparison between the numerical and experimental results for samples 3, 6, and 7 showed that the permeability values predicted by the numerical model were 22.36, 9.96, and 3.93 mL cm⁻² s⁻¹, respectively, while the corresponding experimental values were 30.71, 11.65, and 4.09 mL cm⁻² s⁻¹. The relative errors for these three samples were 27.2, 14.5, and 3.9%, respectively. The reduction in error with increasing fiber diameter indicated that slip effects are more significant at smaller fiber diameters, while the flow approaches the continuum regime as fiber diameter increases. Furthermore, comparison with analytical and empirical models showed that no single model performs uniformly over all ranges of fiber diameter and porosity; therefore, the appropriate permeability model should be selected based on fiber diameter, porosity, and flow regime.