For a next generation positron emission tomograph (PET) detector, quadrant sharing detector or detector using position sensitive photomultiplier tube (PSPMT) as well as conventional block detector will be promising candidates. Since these detectors require different position calculation circuit, it will be a considerable work to develop position calculation circuits for each type of detector. Thus, a flexible personal computer based position calculation system was developed. The system calculates the position by the personal computer event by event basis. The system made it possible to be applicable to many kinds of position calculations for different types of PET detectors.