Because golf is a game in which players often have a wide gulf in talent between friends, a handicap is a method of determining the expected difference in strokes between two players in a round. This can then be used to help level the field, competitively, by removing strokes from the score of the weaker player.
The score that a player shoots on his round is compared with the Course Rating for the set of tees from which the player hit for that course. The Course Rating can be found on the scorecard next to the yardages for the tee color played. To determine a player's score relative to the rating, the rating is subtracted from the player's score. The Course Rating is a reflection of the expected score for a golfer that normally shoots par for a round.
The Slope is a measure of the relative difficulty of a course, in comparison to its rating, for a golfer that normally shoots 18 strokes over par for a round. An average slope is 113, with a higher slope rating reflecting increasing difficulty and a lower rating reflecting decreasing difficulty. The result from subtracting the player's score from the rating (section 1) is multiplied by 113, and divided by the actual slope a given course to find the handicap score for that round.
To find a player's handicap score, multiple rounds of golf must be factored in. The player takes her best recent rounds and adds those handicap scores. That total is divided by the number of rounds added to find an average score. This average score is then multiplied by .96 to find the player's overall handicap.
How Many Rounds to Use
The number of rounds to use depends on how many rounds the player has to score. The most that can be considered are the 20 most recent rounds, in which case the 10 best scores are used. For 19, 18 or 17 rounds, the 10 worst rounds are again discarded, yielding the best 9, 8 or 7 rounds respectively. From there, 1 fewer card is used for every 2 cards the player has, with a minimum of 5 or 6 cards used to find the 1 best score.
Handicap scores are applied by finding the difference in two players scores, and giving the weaker player a set number of strokes at the start of the round, often equal to the difference in handicaps. Each score card ranks the holes from most to least difficult, so that should the players be playing match or skins play, where the hole that a stroke is subtracted from the weaker player's score on is important, the players know when to subtract strokes. A player receiving 7 strokes would take 1 stroke off their score on the 7 hardest holes, for example.