To address the challenges raised by the Internet usage evolution over the last years, the Content-Centric Networking (CCN) has been proposed. One key feature provided by CCN to improve the efficiency of content delivery is the in-network caching, which has major impact on the system performance. In order to improve caching effectiveness in such systems, studying the functioning of CCN in-network storage is required. In this paper, we propose MACS, a Markov chain-based Approximation of CCN caching Systems. We start initially by modeling a single cache node. Afterwards, we extend our model to the case of multiple nodes. A closed-form expression is then derived to define the cache hit probability of each content in the caching system. We compared the results of MACS to those obtained with simulations. The conducted experiments show clearly the accuracy of our model in estimating the cache hit performance of the system.