Abstract Background Tans femoral transcatheter aortic valve implantation (TF-TAVI) was recently the standard treatment option in patient with severe aortic stenosis. All patients undergoing TF-TAVI needed computed tomography angiography (CTA) aorta not only to evaluate entry site but to measure the annulus size to determine the prosthesis valve size. In Siriraj hospital we have protocol to perform Three-dimensional transthoracic echocardiography (3D-TTE) and three-dimensional esophageal echocardiography (3D-TEE) prior to TF-TAVI. We aimed to evaluate the correlation between conventional CTA aorta vs 3D-TEE vs 3D-TTE aortic annulus size. Method and result We performed a cross sectional study in all patients undergone TF-TAVI in our hospital who had all 3 aortic annulus sizes measured by 3 methods: CTA aorta, 3D-TEE vs 3D-TTE during 2015-2023. For 244 patients underwent TAVI, 52 patients were excluded (22 Transapical approach, 10 valve in valve TAVI, 6 not complete annulus measurement, 6 transcarotid, 3 severe AR, etc.) One hundred sixteen patients were female (60.4%) with average age of 83.2 years old. 98% of patients had comorbid disease; hypertension 84%, dyslipidemia 79%, diabetes 47%, coronary artery disease 55% (9% CABG), 2.6% of patients were bicuspid aortic valve. 27% of patients had LVEF less than 55%, average AVA was 0.71 centimeter-square, average mean pressure gradient was 52.5 mmHg. We analyzed the co-relation between these 3 methods by Bland–Altman plot which revealed the Pearson's correlation coefficient (r) between CTA Aorta and 3D-TEE was 0.814 with average difference of 0.68 mm (95% limit of agreement –1.68 - 3.04) and r between CTA Aorta and 3D-TTE was 0.442 with average difference of 0.41 mm (95% limit of agreement –3.82 - 4.63) Conclusion 3D-TTE annulus sizing had a reasonable correlation with CTA annulus sizing (Pearson’s correlation of 0.442) while 3D-TEE annulus sizing had a very high correlation with CTA annulus sizing (Pearson’s correlation of 0.814). In patient which CTA was not available to measure annulus size 3D-TEE annulus sizing might be reasonable method to measure the annulus size for TF-TAVI. Keyword trans femoral transcatheter aortic valve implantation (TF-TAVI), annulus size, three-dimensional transthoracic echocardiography (3D-TTE), three-dimensional esophageal echocardiography (3D-TEE), computed tomography angiography (CTA) aorta