Wireless Local Area Networks (WLANs) are a potential contributor in the future heterogeneous networks (Het-Nets) of 5G Mobile communication systems to ensure extended spectrum usage and higher data rates with better Quality of Service (QoS). Significant network capacity gain can be achieved not only through aggressive reuse of spectrum across the multiple tiers in the network, but also through harnessing an additional spectrum in un-licensed bands by integrating WiFi in the network [1]. Different criteria should be investigated in order to allow both the WiFi APs and the end user to operate on the best suitable channel, where the basic one of those criteria is the "load" of the operating channels. We propose in this paper a novel and accurate algorithm for the estimation of WiFi 802.11n physical channels load through the observation of the non-overlapped channels and estimating as a result the load of the entire physical channels. Once the channels load is estimated using the proposed algorithm, the channel assignment based on the minimal load value is facilitated, thus providing faster response of an AP channel selection and faster end user connection for better Quality of Experience (QoE).