As elevators become more and more indispensable in people's lives, safety has become more of a concern. Overloading is an important contributing factor to elevator accidents. Most existing elevators use weight sensors to determine the total load in an elevator, and those systems can sometimes fail. Additionally, their maintenance is expensive. To avoid such accidents, this design is a proof-of-concept device which can count passengers in real-time at high speed, and can give an alert if the number of people in an elevator is above a threshold. This device can be attached anywhere in the elevator. And compared with existing technology, its implementation cost is low, and maintenance is easy.