Abstract: The present invention is an electronic liquid level monitoring apparatus for a in-ground storage tank. An ultrasonic transducer is disposed in a fill pipe head device which enables proper placement of the ultrasonic transducer in a fixed position relative to the fill pipe of the storage tank and provides a combination for a plurality of different fill pipe diameters. An electronic control measures the length of time from the transmission of the ultrasonic pulse to the receipt of the return echo and then calculates the distance from the ultrasonic transducer to the level of the liquid in the tank. The distance can permit automatic calculation of the amounts of liquid in the tank, using tank parameters stored in a memory as corrected for the speed of sound at the particular temperature measured via a temperature sensor. The apparatus preferably also calculates a volume variance.