A Handicap Index is the USGA’s service mark used to indicate a measurement of a player’s potential ability 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 103 for golfers with two or more eligible Tournament Scores.  
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 Adjusted Gross Score using equitable stroke control
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 71.5 and a USGA Slope Rating of 125:
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:


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:

USGA. 2012. USGA HANDICAP FORMULA. [ONLINE] Available at: http://usga.org/RuleBooks/HandicapSystemManual/Rule10/. [Accessed 08 September 15].
Important Disclaimer: The Sandbagger Golf Handicap Calculator and Tracker is not prepared, approved, or licensed by the and is neither sponsored nor endorsed by USGA. is a registered trademark of the U.S. Golf Association.