A method is presented to measure respiratory motion in mm units based on the scatter of a parallel transmit coil. The respiratory changes in scatter are observed by the local SAR monitor and converted into a respiratory measure through a calibration phase. The newly described measure was compared to the diaphragm position measured in MR images. The standard deviation of the difference between the two was 1.1±0.4 mm across six volunteers. The method was implemented into a free breathing cardiac cine which showed no respiratory artefact when used to gate.