The estimation of grain size (volume) by using computer database of tessellations is explained and demonstrated. As model material was selected an anisotropic material formed by compression-moulded pellets of PVC. The pellets were first covered with carbon paste to highlight borders of grains in final specimen and then moulded; their volumes were exactly known. Standard profile and intercept counts were carried out on the planar sections of the specimen and used to estimate the grain size by means of computer database. The obtained estimates were then compared with the known pellet characteristics. The estimation of grain volume and of other suitable characteristics by inspection of section planes is necessary in opaque materials (e.g. metal alloys, crystalline polymers, ceramics), where their values are inaccessible by direct measurements. The aim of this work is show that the standard approaches can be improved with the help of a suitably prepared computer database.