Caching contents at the network edge is an efficient mean for offloading traffic, reducing latency and improving users' quality-of-experience. In this letter, we focus on aspects of storage-bandwidth tradeoffs in which small cell base stations are distributed according to a homogeneous Poisson point process and cache contents according to a given content popularity distribution, subject to storage constraints. We provide a closed-form expression of the cache-miss probability, defined as the probability of not satisfying users' requests over a given coverage area, as a function of signal-to-interference ratio, cache size, base stations density and content popularity. In particular, it is shown that for a given minimum cache size, the popularity based caching strategy achieves lower outage probability for a given base station density compared to uniform caching. Furthermore, we show that popularity based caching attains better performance in terms of cache-miss probability for the same amount of spectrum.