Due to its large number of degrees of freedom and extensive connection to the brain, the human hand has been used to create channels of communication for a variety of human-machine systems. However, a fundamental question about the hand channel is still unanswered: what is its information capacity? This study aims to provide quantitative indication of effectiveness of the hand as a communication channel. We estimated that per gesture, the thumb and the index finger may deliver at most 10 and 7 bits of information, respectively. Based on this, we derived an upper bound for the information capacity of the hand in gesture-based communication: 150 b/s. Knowing this bound is critical to evaluating the potential and limitation of the hand channel for various forms of human-machine interactions.