Functionality can be implemented to calibrate the output transmit power of a power amplifier of a network device without the use of test equipment. An RF signal can be transmitted at the saturated output power (of a power amplifier) from a transmitter unit to a receiver unit of the network device via a loopback path. A received power of the RF signal received via the loopback path can be measured. The loopback gain associated with the network device is determined based on the saturated output power and the measured received power. The output transmit power can be calibrated by iteratively decreasing the output transmit power by an unknown value, transmitting a new RF signal via the loopback path at the decreased output transmit power, measuring the new received power, and calculating the decreased output transmit power using the loopback gain and the measured new received power.