A method and apparatus for detecting a level of a content in a vessel using an RFID tag. In one embodiment, an RFID tag located on one side of the vessel opposite a side on which the reader is, is interrogated. A reply signal, if any, received from the RFID tag is interpreted to determine the information returned from the RFID tag. The level of the content in the vessel is determined based on the information received from the RFID tag.