In this research software was designed for assessing the inter-yarn zone fabric porosity of Tencel plain weave fabrics in terms of flow of dye liquor by using Matlab. Fabric images were captured at constant light intensity and magnification using an optical microscope and image analysis software. The captured images were first converted into monochrome image and then into binary image at specific threshold value (150). The percentage of white pixels in the binary image were calculated which assessed the fabric porosity in percentage. The loosely woven fabric gives higher percentage of fabric porosity as compared to the tightly woven fabric. This software has potential to calculate the fabric porosity of plain weave fabric manufactured from any type of raw material.