The USGA uses your LAST 20 rounds as the basic guideline to calculate a player's
golf handicap. A factored number of those best rounds are used.
By definition, a USGA Golf Handicap Index is a USGA mark representing the
potential ability of a player on a course of standard difficulty, as determined
by the USGA. 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 golf 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 (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 golf handicap is reduced to the
last whole number. As a formula...
Handicap Differential = ((Adjusted Gross Score - USGA Course
Rating) x 113 / USGA Slope Rating).