An apparatus (10) for calibrating electromagnetic (EM) tracking of an associated ultrasound probe (12) includes a calibration needle (16), an EM tracking device including a field generator (14) and a reference EM sensor (24), an EM sensor (18, 26) on the ultrasound probe and on the calibration needle； at least one processor (50)； and a non-transitory storage medium storing instructions to perform a EM tracking calibration method including: determining a location of the calibration needle in an ultrasound imaging space at a measurement time using the ultrasound probe； determining an EM-tracked location of the calibration needle at the measurement time； and generating a registration relating the location of the calibration needle in the ultrasound imaging space and the EM-tracked location of the calibration needle at the measurement time.
