An apparatus for charging a refrigeration system with a predetermined amount of refrigerant by weight. The apparatus includes a cylinder which is mounted on top of a strain gauge scale that is first filled from a source of refrigrant and then automatically discharged to fill a refrigeration system with a predetermined amount of refrigerant. The system includes solenoid operated valves which are automatically operated for loading the cylinder and charging the refrigeration system. A vacuum pump is also included in the circuit for placing the refrigeration system under a predetermined vacuum prior to the charging operation.