This paper explores the performance of object localization using chipless tags. We show that it is possible to localize a tag (or an object attached to it) by measuring the phase offset between a known position and the position to estimate. This method provides a better accuracy compared to classical ones based on received signal strength indicator (RSSI). We show that sub-millimeter precision can be achieved for distance measurement with a correct localization probability higher than 99%. These results point the way toward new user interfaces using chipless tags which can be con-tactless and 3D.