A method is provided for measuring and controlling the level of an elevated temperature liquid in a container. The electrical voltage signal outputs of a plurality of temperature sensing devices at spaced elevations on the container are converted to digital form. The converted signals are periodically scanned in elevation sequence. A determination is made from the scanned signals of the location of the uppermost sensing means having a converted signal value of sufficient magnitude to indicate a temperature in the wall below the level of liquid in the container. Then a fraction, F, of the spacing between the sensing means, n, and the next above sensing means, n-1, is calculated as a function of the converted signal value, Sn-1. The measured level in the container is calculated as a function of, n, and, F, with respect to their location on the container. Finally, the rate of addition and withdrawal of liquid to and from the container is controlled based on the measured liquid level in the container.