Purpose: To compare the use of sizing implants versus intraoperative volume measurements for individualization of enucleation implant size, and to identify preoperative factors affecting the choice of implant. Methods: In this retrospective observational cohort study, 2 implant sizing methods were compared using clinical records and photographs in 139 patients who underwent enucleation between 2007 and 2016. Results: There was no difference in mean implant (p = 0.6562) or prosthetic (p = 0.1990) enophthalmos between the 2 methods, or when comparing patients with and without conjunctival-Tenons fibrosis. The incidence and severity of superior sulcus deformity was similar between the methods (p = 0.6394). Preoperative phthisis (p < 0.0001) and intraoperative conjunctival-Tenons fibrosis (p = 0.0010) were more common in the sizing implant group. Among all study patients, mean implant size was larger in males (21.3 mm, n = 80) than females (20.7 mm, n = 59) (p = 0.0027). Implants >20 mm were more frequently inserted in patients with a wider Hertel exophthalmometry base (80% of males >95 mm; 77% of females >97 mm). Approximately 21.0% of patients demonstrated ≥8 mm of implant enophthalmos, suggesting an undersized implant. The authors estimate that 11% of patients could have received a sphere larger than 22 mm. Conclusions: Individualization of enucleation implant size can reduce the incidence of anophthalmic socket syndrome. The empirical use of sizing implants provided similar results as intraoperative volumetric measurements, when evaluated by postoperative superior sulcus depth and prosthetic or implant enophthalmos. Preoperative exophthalmometry may facilitate selection of implant size. Preexisting conjunctival-Tenon fascial fibrosis often did not limit implant size and was not associated with a higher prevalence of wound breakdown or implant exposure.