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 the final number to the nearest tenth.

Handicap Differential =
(Adjusted Gross Score - USGA Course Rating) x 113 / USGA Slope Rating


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, the best 10 handicap differentials of the most recent 20 scores are used to calculate the 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, 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 posted. A USGA Handicap Index shall not be issued to a player who has returned fewer than five acceptable scores. The following procedures illustrate how authorized golf associations and golf clubs calculate a player’s Handicap Index.

The procedure for calculating Handicap Indexes is as follows:

i.        Use the table below to determine the number of handicap differentials to use;

PRIVATENumber of
Acceptable Scores

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


Lowest 7


Lowest 8


Lowest 9


Lowest 10

ii.       Determine handicap differentials;

iii.      Average the handicap differentials being used;

iv.     Multiply the average by .96; *

v.       Delete all numbers after the tenths’ digit. Do not round off to the nearest tenth.

* Bonus for Excellence is the incentive that is built into the USGA Handicap System for players to improve their golf games. It is the term used to describe the small percentage below perfect equity that is used to calculate Handicap Indexes (96%). As his Handicap Index improves (gets lower), the player has a slightly better chance of placing high or winning a handicap event.