To prolong battery life of mobile devices, applications often exploit offloading techniques which run computations on remote servers. Unfortunately, the existing offloading techniques do not consider the fact that data transmission time and energy consumption of wireless network interfaces exponentially increase when signal strength decreases. In this paper, we propose an adaptive offloading technique that considers signal strength. Our technique estimates gain (reduced computation time and energy of mobile devices) and loss (increased data transmission time and energy of network interfaces) of offloading depending on signal strength. Based on the estimated gain and loss, our technique determines whether it offloads computations to a server or not. In evaluation, our proposed technique improves performance by 30.1% and saves system-wide energy consumption by 25.0%, on average, compared to the conventional offloading technique that does not consider signal strength.