An automated tool has been developed for generation of permeability predictions for multi-layered unit cells utilising textile modelling techniques. This tool has been used to predict the permeability tensor of a woven textile. Single-layer predictions were carried out and the predicted permeabilities obtained were in close agreement to the permeability behaviour captured experimentally. The tool was used to capture the effects of textile variability on its permeability, isolating the influence of individual parameters. A complete textile sample was also analysed, predicting its permeability map. The concept of estimating the permeability of a textile with variability using an average single unit cell was explored. The prediction tool was also used to study the effect of preform structure on its permeability, including consideration of the number of layers, ply shift and applied compaction.