In the field of industrial ultrasonic testing, ultrasonic thickness measurement (UTM) is a method of performing nondestructive measurement (gauging) of the local thickness of a solid element (typically made of metal, if using ultrasound testing for industrial purposes) basing on the time taken by the ultrasound wave to return to the surface. This type of measurement is typically performed with an ultrasonic thickness gauge.

Ultrasonic waves have been observed to travel through metals at a constant speed characteristic to a given alloy with minor variations due to other factors like temperature.

The wave is usually emitted by a piezoelectric cell or EMAT Sensor that is built into the measurement sensor head and the same sensor is used to record the reflected wave. The sound wave has a spherical pattern of propagation and will undergo different phenomena like multipath reflection or diffraction. The measurement does not need to be affected by these since the first recorded return will normally be the head of the emitted wave travelling at the shortest distance which is equivalent to the thickness of the sample. All other returns can be discarded or might be processed using more complicated strategies.