Abstract: An apparatus for determining the wear of a mold wall during continuous casting of metal by using at least one distance measuring sensor disposed in the mold wall to measure the instantaneous distance from the sensor to the casting. The surface of the casting adjacent the mold wall may be irregular, so the minimum value of the distance between the sensor and casting is stored and used as the current distance between the sensor and the inner mold wall. Mold wear is determined by subtracting the current distance between the sensor and the inner mold wall from the original distance, before the abrasive casting process began. The sensor signals are also used to determine when the mold geometry should be adjusted to compensate for the wear. This is accomplished by storing the maximum distance between the sensor and casting and subtracting the current distance from this maximum, since the maximum distance increases as the casting shrinks away from the mold wall.