The program QMSys THREAD-PD enables the user to determine the pitch diameter of threads when the indicated values are specified as well as to determine the indicated values when the pitch diameter is specified. It is suitable practically for all types of threads: - external and internal - symmetrical and asymmetrical - single-start and multiple Indicated values and pitch diameters are determined using measuring wires or balls by Berndt’s iteration formulae from the publication EA - 10/10 "Guidelines on the Determination of Pitch Diameter of Parallel Thread Gauges by Mechanical Probing". The correction for the measuring force is defined by Lechowski’s methods. The optimum diameter of wires or balls is calculated by the formulae published in EA - 10/10.