A Handicap Index is calculated from the lowest Score Differentials in the scoring record. If a scoring record contains fewer than 20 Score Differentials, the table below is used to determine the number of Score Differentials to be included in the calculation and any adjustment that may apply. Round the result of the calculation to the nearest tenth.
Number of Score Differentials in scoring record 
Score Differential(s) to be used in calculation of Handicap Index 
Adjustment 

3 
Lowest 1 
2.0 
4 
Lowest 1 
1.0 
5 
Lowest 1 
0 
6 
Average of lowest 2 
1.0 
7 or 8 
Average of lowest 2 
0 
9 to 11 
Average of lowest 3 
0 
12 to 14 
Average of lowest 4 
0 
15 or 16 
Average of lowest 5 
0 
17 or 18 
Average of lowest 6 
0 
19 
Average of lowest 7 
0 
20 
Average of lowest 8 
0 
Allocation of an Initial Handicap Index
Based on any additional evidence available about a player’s demonstrated ability, a Handicap Committee may modify a player’s initial Handicap Index upward or downward (see Rule 7.1a Conducting a Handicap Review and Adjusting a Handicap Index).
Rule 5.2a Interpretations: 

5.2a/1 – Modification of a Player’s Initial Handicap Index Due to Evidence of Previous Ability A player submits three scores to obtain an initial Handicap Index, which result in calculated Score Differentials of 15.3, 15.2 and 16.6. This would result in an initial Handicap Index of:
The Handicap Committee is aware that the player, who is rejoining a golf club after many years out of the game, had played well as a junior golfer and maintained a Handicap Index of around 8.0. Based on the evidence available, the Handicap Committee may adjust the player’s calculated initial Handicap Index to better reflect their previously demonstrated ability. 5.2a/2 – Modification of a Player’s Initial Handicap Index When Subsequent Scores Are Significantly Different Than Expected A player submits three scores to obtain an initial Handicap Index, which result in calculated Score Differentials of 40.7, 42.4 and 36.1. This would result in an initial Handicap Index of:
The player then goes on to submit three more scores which result in calculated Score Differentials of 45.9, 43.6 and 45.0. After these six scores, the player’s Handicap Index would be:


In reviewing the player’s calculated Handicap Index against their scores, the Handicap Committee may conclude in this case that the 1 adjustment should be removed to ensure the calculated Handicap Index better reflects the player’s ability. 
A Handicap Index is calculated from the lowest Score Differentials in the scoring record. If a scoring record contains at least 20 Score Differentials, the procedure for calculating a Handicap Index is:
(See Rule 5.8 Limit on Upward Movement of a Handicap Index.)
When there are 20 Score Differentials in a player’s scoring record and the Handicap Index calculates as a negative figure, this represents a plus Handicap Index.
When a player’s initial Handicap Index calculates at the lower end of the handicap range for both men and women, the Handicap Committee must follow any procedures established by the Authorized Association before issuing a Handicap Index below a specified level (see Rule 5.2a For Fewer Than 20 Scores).