Abstract : In this paper, a new way of detecting the level of fluids, remotely, using a chipless RFID sensor is investigated for the first time. For the sake of comparison, a classical RFID tag applied on a box is used to measure a water level thanks to the variation of the threshold transmitting power. Then a chipless RFID sensor design based on multiple resonators etched on a flexible laminate is introduced. In this case, the operating frequencies are between 2.5 and 4 GHz. A comparison is drawn between these two techniques in terms of unit cost and performance.