Any measurement device needs to be calibrated to ensure that the signal output is in some known relation to the input. This is especially true for particle sensors sent into space. Those instruments can usually not be retrieved for recalibration in case questions about the validity of the measurements occur. Also, these in-situ space instruments are sometimes flown to locations where no other instrument has been before (e.g. Pluto). We will describe typical calibration systems for particle instruments for spacecraft such as plasma sensors, mass spectrometers, energetic neutral atom imagers or solid-state detector telescopes spanning the energy range from 0 eV to 10 MeV. We will touch upon selection for beam sources and beam monitors.