Tachometer is a device that measures the rotational speed of any shaft or disc. The unit of the measurement is usually revolutions per minute or RPM. The traditional method of measuring RPM of a rotating shaft was based on velocity feedback concept where a dc generator is hooked to the rotating shaft so that the voltage induced across the generator’s terminals is proportional to the speed of the shaft. Today, we are going to make a digital tachometer based on a Raspberry Pi that requires no physical contact with the rotating shaft to measure its rotational speed. The physical contact is avoided by using an optical detection technique that requires an infrared light emitting diode in conjunction with a photo detecting diode. Raspberry pi is a single board computer which we are using to calculate the speed which is programmed using Python. This tachometer can measure speeds up to without being in contact with the shaft. The result is shown on a web page using a small network area.