An electronic overload current breaker supports arc-fault and ground-fault (AFGF) detection along with built-in shunt calibration (BISC™). The breaker may include a current sensing shunt and a control circuit electrically coupled to the current sensing shunt. This control circuit is configured to calibrate the current sensing shunt in response to application of a calibration current to the breaker. The control circuit can: (i) determine a magnitude of the calibration current applied to the breaker, (ii) map the magnitude of the calibration current to a first one of a plurality of current ratings for the breaker, and (iii) set the breaker to monitor overload conditions at the first one of the plurality of current ratings. The plurality of current ratings for the breaker can be less than the magnitude of the calibration current.