The present invention comprises a system and method for determining an estimated position of a wireless mobile client device operating in a communications environment covered by a wireless local area network. The received signal strength of the wireless mobile client device is measured by one or more access points serving devices in the communications environment. In a preferred embodiment, the error between the received signal strength measured by the access points and the expected received signal strength at a plurality of locations in the communications environment is calculated. The location of the device is determined from the error.