The minimum diameter of a golf ball is 1.68 inches as specified by the United States Golf Association, so the circumference is 5.28 inches. A regulation ball weighs 1.62 ounces.
Prior to 1990, the Royal and Ancient Golf Club of Saint Andrews allowed a smaller ball in British tournament play. While weighing the same as the American ball, the British ball was only 1.62 inches in diameter or 5.09 inches in circumference. The smaller size meant less drag and made for longer drives and less interference from the wind. In 1974, the R and A outlawed the smaller ball for British Open Tournaments, and in 1990 it adopted 1.68 inches in diameter as its standard minimum size.
