This paper presents the problem of the impact that noise has on the result of measuring roundness deviation. Introduction describes the notion of roundness, characteristical/typical errors in roundness and the use of roundness as a tolerance in technical designs. The following section shows how roundness deviation is measured and the procedure of measuring roundness deviation in Laboratory for Precision Length Measurements (LFSB) at Faculty of Mechanical Engineering and Naval Architecture (FSB). After that, the parameters describing the state of roundness are presented in detail. Each of these parameters refers to a reference circle that is associated to a measurement object. There is also shown a procedure for setting the most suitable geometry - the procedure for setting replacement geometries from the actual data collected by measuring instruments. Furthermore, two methods by which noise can be eliminated when measuring deviation from roundness are described. The first method reduces noise by extrapolating one roundness parameter, while the second method uses a Fourier transformation and generates a reduced noise profile by conducting several measurements through a set of equations. The next section presents a detailed way of removing the eccentricity of an object, which is important because the eccentricity is directly affected by the measurer themself. With decreased eccentricity, measurement results will come out more accurate. There is also a noise removal presented by the method of extrapolation of the roundness parameter. This procedure is simulated in the software package Matlab. The same method was conducted by simulating three examples with a different number of measurements. The results presented in the tables show that the impact of noise is deacreased with increasing number of measurements. It is also evident that four repeated measurements are (ne treba good) enough for sufficiently reliable results. By increasing the number of measurements, the noise is reduced, although it can not be completely eliminated. The last part of this paper shows the extrapolation of the circularity parameter conducted on the actual measurement results obtained in the LFSB, their analysis and conclusion.