Vacuum technological process can be performed using specific equipment and in order to reach desired result it is essential to focus on the pressure inside a vacuum chamber. Pressure can be measured using various types of vacuum gauges with different operating principles. During technological process a high level of vacuum should be reached, therefore it's essential to select proper gauge for reliable and correct vacuum measurements. One particular vacuum gauge cannot be selected for broad vacuum range because due to physical reasons it is impossible to construct vacuum gauge, which can be reliable and carry precise pressure measurements in the entire range of vacuum. Gauge operating principles and pressure measuring ranges are not the only factor that affects vacuum gauge selection process. Vacuum gauge operating conditions influence measurement accuracy due to high risk of contamination, vibrations, temperature, etc. Vacuum gauge mounting on the chamber is also one of the main factors for accurate pressure measurements. This paper is focused on analysis of selection criteria for vacuum gauges and its accuracy. The analysis of different type vacuum gauges is given, in order to understand operating principles, their main advantages and disadvantages. Accuracy and repeatability of several vacuum gauges are compared. As an example of the vacuum gauge accuracy problem one specific experiment is given. Diaphragm and ionization gauges were selected for experiment due to their pressure diapason, accuracy, repeatability and ionization gas correction options. Those vacuum gauges are most commonly used for vacuum technological processes. Main idea of the experiment is to show the consequences of unreliable and uncalibrated ionization gauge