<p>Outer Engineered Cementitious Composites (ECC) jackets have been proven to significantly enhance the seismic performance of columns while facilitating rapid damage repair and jacket replacement. To promote its engineering application, there is still a lack of a complete calculation model for rapid estimation of strength and deformation, as well as an economic model for feasibility analysis, and no comparative analysis with traditional reinforcement methods has been conducted either. This study proposed a strength calculation model for outer ECC jacketed composite columns based on the “Equivalent Stiffness Method,” validated against the sectional integration method, finite element analysis (FEA), and experimental results. The FEA considered two jacket thicknesses, three jacket heights, and two equivalent cross-sections. Additionally, an economic evaluation index was introduced to assess the feasibility of applying outer ECC jacketed composite columns, along with a proportional reduction factor to account for the influence of ECC jacket height on the confinement of core concrete. Based on the theories of elastic mechanics and material mechanics, a displacement calculation model was proposed, and the skeleton curve model was modified. The results showed that the computational error of the mechanical model was less than 10%. Compared to ordinary concrete columns, outer ECC jacketed composite columns can more than double the energy dissipation. While increasing the column cross-section achieved similar bearing capacity, its ductility coefficient and energy dissipation were only half and 60% of the ECC jacketed columns, respectively, with a lower economic evaluation index. This study provides technical guidance for engineering applications and theoretical support for the design optimization of structures.</p>