Calculation of Handicap Index | Mapperley Golf Club

Handicap Index is a measure of a player's demonstrated ability calculated against the Slope Rating of a golf course of standard playing difficulty:

It represents a golfer's Course Handicap on a course with a Neutral Slope Rating of 113
It is calculated as a rolling average of the lowest 8 from the last 20 Score Differentials. Each time a new score is submitted the average of the lowest 8 from the last 20 is re-calculated, which may or may not lead to a change of Handicap Index
There are additional adjustments for Exceptional Scores and safeguards (Caps) to ensure that a player's handicap does not rise too quickly when the player is going through a spell of poor form

Score Differential

When a player submits an Acceptable Score, the Score Differential for the round is calculated by first comparing the Adjusted Gross Score with the Course Rating and taking into account any PCC (Playing Condition Calculation) adjustments for the day. The differential is multiplied by 113 and divided by the Slope Rating of the course played to determine the equivalent differential on a course with a Neutral Slope Rating of 113. For example:

A woman playing the Red tees at Mapperley (Course Rating 72.4, Slope Rating 128) has an Adjusted Gross Score of 90. The PCC for the day is 1.

Score Differential = [ 90 - 72.4 - 1.0 ] x [ 113 / 128 ] = 14.7
A man playing the Yellow Alternate tees at Mapperley (Course Rating 68.3, Slope Rating 120) has an Adjusted Gross Score of 90. The PCC for the day is 0.

Score Differential = [ 90 - 68.3 - 0.0 ] x [ 113 / 120 ] = 20.4

Each new Score Differential is added to the player's Scoring Record and used to calculate their new Handicap Index.

Low Handicap Index (LHI)

A player's lowest Handicap Index during the last 12 months is used as an Anchor Point to limit increases in Handicap Index

Soft CAP:
Potential increases of Handicap Index to a figure greater than (LHI + 3) are limited by half the amount over three, e.g. 5 is limited to 4, 6 is limited to 4.5, etc.
Hard CAP:
The maximum that the Handicap Index can increase to is (LHI + 5).

Exceptional Scores

Adjustments to the Handicap Index are made after a very low score has been posted:

A reduction of -1 for scores between 7 and 9 below Handicap Index
A reduction of -2 for scores 10 or more below Handicap Index
The reduction is applied to the last 20 scores on the Scoring Record and drops off gradually over the next 20 rounds.

Videos

You can view more about Handicap Index in the following videos:

Handicap Index: Basis of Calculation

Handicap Index: Daily Revisions

New Player Handicaps

A New Player's Handicap Index is initially allocated at 2 less than the best of the Score Differentials from 3 x 18 hole cards submitted. Cards can be submitted as 6 x 9 hole or some other combination. Subsequent Handicap Index calculations change as more scores are entered:

3 scores: lowest score -2
4 scores: lowest score -1
5 scores: lowest score
6 scores: average of lowest 2 scores -1
7 to 8 scores: average of lowest 2 scores
9 to 11 scores: average of lowest 3 scores
12 to 14 scores: average of lowest 4 scores
15 to 16 scores: average of lowest 5 scores
17 to 18 scores: average of lowest 6 scores
19 scores: average of lowest 7 scores
20 scores: average of lowest 8 scores