Abstract: Wireless Mesh Networks (WMNs) being an emerging technology has in recent years received research focus. Considered to be the next step in the evolution of wireless networks, WMNs promises greater flexibility, reliability and performance. In wireless mesh networks, there are multiple potential paths exist between any pair of mesh stations; as each route uses a different set of links with varying link quality, these routes may have different throughputs. Routing protocol selects the route with the best possible throughput. Routing metrics used by routing protocols decides which route to use between pair of nodes. A routing metric is a transaction that provides a number assigned to each route then the routing protocol selects the route with the best one. Our prime concern to design routing metric referred RETT: Revised Expected Transmission Time. Our proposed metric can be able to estimate the end-to-end delay experienced by packet for the available paths to enable the routing protocol to select the best path. RETT considers the link rate, number of retransmissions, control overhead, etc. We consider the control overhead of sending a data packet that includes the time to send a RTS, CTS, DIFS, SIFS. So, the metric show the exact transmission time of a packet from one node to another. It modified the ETT routing metric and represents a new way to calculate expected transmission time