Disclosed is a method for determining the exact center of a coin that is introduced into a coin acceptor unit. According to said method, the probable center is determined by means of a sensor array, and the image of the coin that is to be examined is recorded. The peripheral area of the coin around the probable center and the zone beyond the probable edge thereof are developed using said image of the coin, the edge of the coin being represented as an approximately sinusoidal line when the probable center shifts to the exact center. The exact center is determined by analyzing the at least sinusoidal line using the amplitude and the phase angle from a selected starting point.