The Center of Gravity (CG) controls a number of effects that are important in determining the performance of golf clubs. (NOTE: The club “sweet spot” is not its “center of gravity”. These are two distinct principles.) The CG of a golf club head is the one small point no bigger than the sharp end of a pin that represents an intersection of all the possible balance points of it. The center of gravity position in the club head is initially controlled by the height, width and breadth of the head. After that, it is influenced by how much of the head’s weight is placed in different areas of the club head.
Because the center of gravity is a single point inside the club head, its location has to be defined in 3-dimensions. This means that a club head has a vertical CG location (how high up in the head the CG is from the sole). It also has a horizontal CG location (how far over it is from the center of the shaft in the hosel of the head). The center of gravity is also defined by how far back from the club face it is located.
In a golf club head, the CG can be determined by balancing the head on its face, sole, or any place on the head; the intersection inside of the head of all these different balance points is the center of gravity.