Abstract: An engine tachometer device for determining the revolutions per minute of an engine which generates sparks and has a predetermined configuration. A computer memory is utilized for storing engine configuration data. The engine configuration data associates engine configurations with predetermined equations. An engine configuration selector selects from the computer memory one of the engine configurations which is indicative of the configuration of the engine. An engine characteristic calculator which is connected to the engine and to the engine configuration selector and to the computer memory determines the revolutions per minute of the engine based upon the generated sparks and upon the equation associated with the selected engine configuration. Accordingly, the device accurately monitors the RPM of all configurations of engines.