The aim of this master's thesis is to create a function library that can be used to determine deviations from roundness based on measured data. The theoretical part of the thesis explains what roundness and deviations from roundness are, the parameters of roundness, the methods used to measure roundness along with their advantages and disadvantages, and why and which method was chosen for measuring the roundness of the test sample. The selected method is described in detail with an emphasis on the errors that may occur during measurements of the test sample. It also describes how these errors are eliminated through signal processing and sample positioning. The experimental part is related to the processing and filtration of the collected data; a function library was created that uses the Fourier transform to process and filter the data and calculates the roundness parameters. The program code of the library is described in detail, with explanations of the functions used. An additional program was created to generate simulated roundness measurement data to verify the accuracy and validation of the developed library. Additionally, roundness measurements were performed in the Laboratory for Precision Length Measurements at the Faculty of Mechanical Engineering and Naval Architecture, on the Mahr MMQ3 device. The data was analyzed and filtered using the developed roundness measurement library. At the very end of the thesis, a conclusion is provided based on the analysis of the obtained results.