The analysis of ossification points plays a considerable role in forensic age estimation. Although traditional methods are still in use, researchers are working on different age estimation procedures especially within the development of radiologic methods. One of these methods is to define spheno-occipital synchondrosis fusion degree. Spheno-occipital synchondrosis, an important growth point on cranial base, provides noteworthy information about age estimation through its late stage ossification nature. This study aimed to investigate spheno-occipital synchondrosis fusion degree for age estimation in the Turkish population. In our study, 1-mm-sectioned computed tomography images of 638 (399 men and 139 women) subjects within the age of 10 to 25 years were retrospectively examined. It is stated in our study that spheno-occipital syncondrosis fusion begins superiorly and progresses inferiorly until it is completed. Spheno-occipital syncondrosis is known to be totally open at the mean (SD) age of 11.5 (1.5) years in men and 10.7 (0.8) years in women. In addition, fusion degree is known to be increased with age. Fusion starts approximately 2 years earlier in women than in men, and the process of fusion completes at the age of 17 years in both sexes. An analysis of fusion degree between sex groups showed significance at the age of 11 to 15 years, and Spearman rank correlations indicate a significant positive relationship between age and degree of spheno-occipital fusion (P < 0.001; men, ρ = 0.714; women, ρ = 0.698). Consequently, 5-staged analysis of spheno-occipital synchondrosis fusion degree in use with 1-mm computed tomography images will be helpful for age estimation between 11 and 17 years.