Circular open-ring resonators (ORR) merit special attention in many applications. They form the backbone of metamaterials. Therefore, a simple and accurate LC model is required to allow the behavior of the structure to be analyzed from the geometric parameters. In this paper, we propose an analytical model to compute the LC resonant frequency response. The model is verified numerically and experimentally in mmwave frequency range with a normal incidence illumination. Moreover, the effect of the geometric parameters has been alsostudied. The results are very motivating and a good agreement is obtained.