The dimensional and geometrical specifications control of a mechanical part is commonly done using a coordinate measuring machine. Collecting and processing measurement data through a probe, it allows measuring the conformity of the part according to specific tolerances. An accurate estimation of the uncertainty of measurement is critical; it is within this framework that our study is oriented; we aim to estimate the measurement uncertainty of parallelism error using the Guide to the Expression of Measurement Uncertainty (GUM), then we will proceed to a Monte Carlo simulation to compare the obtained uncertainty, we will then proceed to an inter-laboratory comparison to validate our model. Our contribution is based on a more detailed and precise estimation of the uncertainties of the measurement process taking into accounts the calibration of the machine and the propagation of uncertainties.