This study states that Aortic endograft sizing for endovascular aneurysm repair (EVAR) is not consistent despite published instructions for use (IFU). By analyzing data obtained from the Global Registry for Endovascular Aortic Treatment (GREAT), we sought to identify factors associated with oversizing and undersizing; to determine sex influence on sizing; and to examine sizing effects on endoleak, reintervention, and mortality. All patients enrolled in GREAT undergoing EVAR were included for analysis. Proximal and distal aortic landing zones were compared with device implanted to assess sizing as related to IFU. The χ2 and Fisher exact tests were used to evaluate associations between IFU sizing and demographics. Logistic regression modeling was used to identify predictors of outside IFU sizing. Cox proportional hazards regression analyzed the relationship between sizing and endoleak, device-related reinterventions, and all-cause/aortic mortality. There were 3607 participants enrolled in GREAT as of March 2020. Of these, 1896 (53%) were within IFU for sizing, 791 (22%) were oversized, 540 (15%) were undersized, and 380 (10%) had both oversized and undersized components.