We present Cross-layer Unicast Transmission Time (X-UTT), a MAC-aware load-independent link cost metric for 802.11based wireless mesh networks. X-UTT utilizes information acquired from a network-layer unicast probing system and a MAC-layer monitoring system. It is designed to capture the wireless link capacity and be independent of the load induced by self-interference and cross-interference in a mesh network. We present experiments that validate these two properties on our mesh network testbed. These properties can be further exploited in the design of stable path metrics and routing protocols for wireless mesh networks.