A description of the USGA® Handicap-Index is that usgaindex is a golf handicap index term which represents the potential ability of a golfer on a golf course of standard or typical playing difficulty, as determined by the USGA®. Potential playing ability is measured by a player's best course 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% of the average of the best handicap differentials, and applying USGA Rules Handicap Section 10-3 for golfers with two or more eligible tournament scores.

A handicap differential is computed from four elements. Those are adjusted gross score, USGA Course Rating, USGA Course Slope Rating and 113 (the slope rating of a course of standard difficulty).

To determine the handicap differential (known as the Index), subtract the USGA® Course Rating from the adjusted gross score; multiply the difference by 113; then divide the resulting number by the USGA Course Slope Rating. Round the final number to the nearest tenth. A factored handicap is reduced to the last whole number. As a formula,

Handicap Differential = ((Adjusted Gross Score - U.S.Golf Association Golf Course Rating) x 113 / USGA® Slope Rating)