In timber production, there is a need to select the right log for a given end-product. To achieve this objective, individual tree characteristics (total height, diameter at breast height and age) and external measurements made on the log shape were combined. In this study, three possible methods are analyzed to assess the number of annual rings for a given Picea abies (L.) Karst. log using modelling. The first method consists of finding a link between the number of rings and the size, the taper and the location of the log in the tree. The second one is based on the log location in the tree and the use of an height-age growth model. The third involves the whorl location inside the log and the use of an individual height-age growth model. The three methods are compared on the basis of the amount of data required by each and error analysis.