Rules for all sorts of Golf betting games (Thanks to Tim).
A USGA Handicap Index is a number that represents the potential ability of a player on a course of standard difficulty. Potential ability is measured by a player's best scores, and is expressed as a number taken to one decimal place. These scores are identified by calculating the handicap differential for each score. The USGA Handicap Index is calculated by taking 96 percent of the average of the best handicap differentials, and applying section 10-3 for golfers with two or more eligible tournament scores.
10-1 How to Determine Handicap differentials
A handicap differential is computed from four elements: adjusted gross score, USGA Course Rating, USGA slope rating, and 113 ( The slope rating of a course of standard difficulty ). To determine the handicap differential, subtract the USGA Course rating from the adjusted gross score; multiply the difference by 113; then divide the resulting number by the USGA slope Rating. round off the final number to the nearest tenth.
Handicap Differential = (Adjusted gross score-USGA Course Rating) x 113 / USGA Slope Rating.
a) Plus Handicap Differential
When the adjusted gross score is higher than the USGA Course Rating, the handicap differential is a positive number. Following is an example for determining a differential using an adjusted gross score of 95 made on a course with a USGA Course Rating of 67.3 and a USGA Slope Rating of 111:
Adjusted Gross Score - USGA Course Rating: 95 - 67.3 = 27.7
Difference x Standard Slope: 27.7 x 113 = 3130.1
Result / USGA slope Rating: 3130.1 / 111 = 28.199
Handicap
Differential ( Rounded ): 28.2
b) Minus Handicap Differential
When the adjusted gross score is lower than the USGA Course Rating, the handicap differential is a negative number. Following is an example for determining a differential using an adjusted gross score of 69 made on a course with a USGA Course Rating of 71.5 and a USGA Slope Rating Of 125:
Adjusted Gross Score - USGA Course Rating:69 - 71.5 = -2.5
Difference x standard Slope: -2.5 x 113 = -282.5
Result / USGA slope Rating: -282.5 / 125 = -2.26
Handicap Differential ( Rounded
): -2.3
10-2 USGA Handicap Index Formula
The USGA Handicap
Index Formula is based on the best handicap differentials in a player's scoring record. If
a player's scoring record contains 20 or more scores, then the best 10 handicap
differentials of the most recent 20 scores are used to calculate his USGA Handicap Index.
The percentage of scores used in a scoring record decreases from the maximum of the best
50 percent as the number of scores in the scoring record decreases. If the scoring record
contains 9 or 10 scores, then only the best three scores ( 30 to 33 percent ) in the
scoring record will be used. Thus, the accuracy of a player's Handicap Index is directly
proportional to the number of acceptable scores he has posted. A USGA Handicap Index shall
not be issued to a player who has returned fewer than five acceptable scores. The
following procedure illustrates how to calculate a player's Handicap Index if the number
of acceptable scores in the player's record is less than 20.
The procedure for calculating Handicap Indexes is as
follows:
(I) Use the
following table to determine the number of handicap differentials to use:
| Number of acceptable Scores | Differentials to be used |
| 5 or 6 | Lowest 1 |
| 7 or 8 | Lowest 2 |
| 9 or 10 | Lowest 3 |
| 11 or 12 | Lowest 4 |
| 13 or 14 | Lowest 5 |
| 15 or 16 | Lowest 6 |
| 17 | Lowest 7 |
| 18 | Lowest 8 |
| 19 | Lowest 9 |
| 20 | Lowest 10 |
( ii ) Determine the Handicap Differentials;
( iii ) Average the Handicap Differentials being used;
( iv ) Multiply the average by 0.96;
( v ) Delete all numbers after the tenth digit. Do not round off to the
nearest tenth.
Example 1: 11 scores available
Total of lowest 4 handicap
differentials: 103.5
Average ( 103.5 divided by 4
): 25.875
Multiply average
by 0.96: 24.84
Delete digits
after tenths: 24.8
USGA Handicap Index: 24.8
