Abstract—In this paper, we present a square-root inverse sliding window filter (SR-ISWF) for vision-aided inertial nav-igation systems (VINS). While regular inverse filters suffer from numerical issues, employing their square-root equivalent enables the usage of single-precision number representations, thus achieving considerable speed ups as compared to double-precision alternatives on resource-constrained mobile platforms. Besides a detailed description of the SR-ISWF for VINS, which focuses on the numerical procedures that enable exploiting the problem’s structure for gaining in efficiency, this paper presents a thorough validation of the algorithm’s processing requirements and achieved accuracy. In particular, experiments are conduct-ed using a commercial-grade cell phone, where the proposed algorithm is shown to achieve the same level of estimation accuracy, when compared to state-of-the-art VINS algorithms,