BACKGROUND: Aortic valve calcium score (AVCa) measured on noncontrast computed tomography (CT) is well-established for grading aortic stenosis (AS) severity. However, thresholds for AVCa measured on contrast CT remain uncertain. We evaluated correlations, associated factors, and severity thresholds of AVCa measured on contrast CT against transthoracic echocardiography (TTE) measures of AS. METHODS: Patients with native AS undergoing transcatheter aortic valve replacement evaluation from 2019 to 2020 who underwent TTE and contrast-enhanced CT were retrospectively studied (n=1035, age 79±9 years, 429 (41.5%) women, 906 (87.5%) severe and 129 (12.5%) moderate AS by TTE). AVCa was measured using the modified Agatston method with the minimum threshold of 4 SD above the mean ascending aorta blood pool Hounsfield units. Receiver-operating characteristics analysis and Youden index were used to define sex-specific optimal AVCa thresholds for identifying severe AS defined by TTE (aortic valve area by continuity equation ≤1.0 cm RESULTS: Mean aortic valve area on TTE was 0.79±0.21 cm CONCLUSIONS: AVCa by contrast CT is a useful tool for identifying severe AS by TTE, with sex-specific thresholds for severe AS identified. Further studies are necessary to externally validate our findings and evaluate their prognostic significance.