The Game of Golf
A hole is classified by its par, which gives an indication of the number of strokes a skilled golfer may be expected to need to complete play of the hole. The primary factor for classifying the par of a relatively straight, hazard-free hole is the distance from the tee to the green, and calculates the number of strokes a skilled golfer is expected to require to reach the green with an additional allowance of 2 putts. As such, the minimum par of any hole is 3; one stroke for the tee shot and two putts. Par 3, 4 and 5 holes are commonplace on golf courses; far more rarely, courses may feature par-6 and even par-7 holes.
For men, a typical par-3 hole is less than 250 yards (230 m) in length, with a par-4 hole ranging between 251–450 yards (230–411 m), and a par-5 hole being longer than 450 yards (410 m); for women these boundaries are lower, and for professionals they are much increased. The rare par-6s can stretch well over 650 yards (590 m). These distances are based on the typical scratch golfer's drive distance of between 240 and 280 yards (220 and 260 m). Although length is the primary factor in calculating par, other factors are taken into account; however the number of strokes a scratch golfer should take to make the green remains foremost. Factors affecting the calculation include altitude, gradient of the land from the tee to green, and forced "lay-ups" due to dog-legs (sharp bends) or obstacles (e.g. bunkers, water hazards).
Getting the ball onto the green in two strokes less than par, and hence meeting the par calculation criteria, is called making "green in regulation" or GIR. Missing a GIR does not necessarily mean a golfer will not make par, but it does make doing so more difficult as it reduces the number of putts available; conversely, making a GIR does not guarantee a par, as the player might require three or more putts to "hole out". Professional golfers typically make between 60% and 70% of greens in regulation.
Eighteen-hole courses typically total to an overall par score of 70 to 72 for a complete round; with most holes having a par of 4, and a smaller number of par-3 and par-5 holes. Additionally, courses may be classified according to their play difficulty, which may be used to calculate a golfer's handicap. The two primary difficulty ratings in the U.S. are the Course Rating, which is the expected score for a zero-handicap "scratch golfer", and the Slope Rating, which is a measure of how much worse a "bogey golfer" (handicap around 20) would be expected to play than a "scratch golfer" relative to their handicap.
