The method used is an algorithm to find the closest value from the lifting load chart of a crane car. In this paper, a prototype LMI has been made on a mobile crane based on a microcontroller that can provide value. Mobile cranes have a high accident potential when compared to tower cranes, and this is because mobile cranes have high mobility. This tool has a very important role because it provides accessible information to the operator about the safe working load (SWL) that the crane can lift. A load moment indicator (LMI) is an electronic device on heavy equipment cranes that can provide information and a warning system to operators in the event of an overload during the lifting load process.