This paper can be divided into five main parts in which the following numbers are explained: 1. What is roundness and why it is important to measure out of roundness; 2. Procedure of out of roundness measurement; 3. Standards used for roundness measuring instrument calibration; 4. Most commonly used methods of roundness measuring instrument calibration and a list of scientific papers; 5. Proposal of a new stylus calibration method of roundness measuring instrument. In the first part, the term roundness is defined. Also, the importance of out of roundness measurement is explained. Several typical forms of roundness errors are listed, as well as the influence of roundness on the functionality of an object. In the second part, two types of roundness measuring instruments and numerical methods that are used for roundness determination are explained. Also, the procedure for roundness measurement in the Laboratory for Precise Measurement of Length (LFSB) of the Faculty of Mechanical Engineering and Naval Architecture is demonstrated, step by step. The third part refers to the establishment of a traceability chain. Also, the most common standards used for calibration of the roundness measuring instrument are illustrated. The fourth part describes the most commonly used methods of calibration of roundness measuring instruments and a list of scientific papers related to this topic that can be used for further research. In the last part, the current method of static calibration of the roundness measuring instrument in the LFSB is described, and a new dynamic method of instrument calibration is proposed.