The invention relates to a position and load measurement system for an elevator which system is going to be installed in an elevator car to obtain car position data and car load data, which position and load measurement system comprises at least one sensor mounted in the elevator car. The position and load measurement system comprises: a passenger sensor scanning the car interior and/or the car door area; a load signal processing unit connected to the passenger sensor for generating car load data, an acceleration sensor and/or magnetometer, a position signal processing unit connected to the acceleration sensor and/or magnetometer for generating car position data, and a data link for transmitting the output signals of the load signal processing unit and the position signal processing unit to an elevator control unit. The invention provides improved car load and car position data, particularly in connection with an overlay modernization of an existing elevator system.