A Handicap Index is a 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 Handicap Index is calculated by taking 96 percent of the average of the best handicap differentials, and applying rule 6.1 of the world handicap system.  
How to Determine Handicap Differentials  
A handicap differential is computed from four elements: adjusted gross score, Course Rating, Slope Rating and 113 (the Slope Rating of a course of standard difficulty). To determine the handicap differential, subtract the Course Rating from the adjusted gross score; multiply the difference by 113; then divide the resulting number by the Slope Rating. Round the final number to the nearest tenth.
Handicap Differential = WHS Adjusted Gross Score. An adjusted gross score is determined by limiting the maximum score on a hole to net par plus two strokes (?net double bogey?). This scoring limit is familiar to golfers playing a Stableford format and now applies to all forms of play. If a player is allocated one stroke on a par 5 hole, You can take no more than a net doublebogey, no matter your ability. a.Plus Handicap Differential When the adjusted gross score is higher than the 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 Course Rating of 71.5 and a Slope Rating of 125:
b. Minus Handicap Differential When the adjusted gross score is lower than the 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 Course Rating of 71.5 and a Slope Rating of 125:


USGA Handicap Index Formula  
The 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 8 handicap differentials of the most recent 20 scores are used to calculate the Handicap Index. A Handicap Index shall not be issued to a player who has returned fewer than 3 acceptable scores.
The procedure for calculating Handicap Indexes is as follows:
Example 1: Fewer than 20 scores (13 scores available).

Important Disclaimer: The Sandbagger Golf Handicap Calculator and Tracker is not prepared, approved, or licensed by the and is neither sponsored nor endorsed by WHA.