A standard full round of golf consists of 18 holes. These holes are normally divided into a front nine, holes 1 through 9, and a back nine, holes 10 through 18.
The 18-hole tradition is strongly associated with the Old Course at St Andrews in Scotland. In 1764, several of its original holes were combined, leaving an 18-hole circuit that golfers played outward and then back toward the clubhouse. That layout helped establish the format that became standard internationally.
Eighteen holes describes the length of a conventional round, not the number of strokes a player should take. A course’s par may commonly be around 70 to 72, but it varies by layout. Nine-hole courses are also legitimate and popular, and players may complete two loops to play an 18-hole round.