WiFi is the prevalent wireless access technology in local area deployments and is expected to play a major role in a mobile operator’s data offloading strategy. As a result, having simple tools that are able to assess the offloading potential of IEEE 802.11 networks is vital. In this paper, we propose a simple closed-form solution to calculate down- and uplink throughput values per user under full-buffer traffic when small WiFi cells are used to offload macrocells. Extensive measurement campaigns and simulation results demonstrate that there is an excellent quantitative match between analytical model and data despite the simplicity of the former. Finally, in light of our observations we discuss some of the fundamental technological limitations that may have a significant impact on the future of small cells.