To assure the safety of a nuclear reactor during operation, it is important to know the control rod worth, which is an absolute value of negative reactivity induced by a control rod insertion. The measurement for the control rod worth is known as the control rod calibration. In addition to the safety viewpoints, the control rod calibration is important also in conducting other reactor physics experiments since various reactivity effects can be quantified from the known control rod worth. To measure the control rod worth during this experimental program at KUCA, the stable period method, the compensation method, and the rod drop method are employed. Details of these methods are described in this chapter.