How to Calculate a USGA Handicap Index

How to Calculate a USGA Handicap Index  
A USGA Handicap Index is calculated by taking 96% of the average of the best handicap differentials. A handicap differential is computed from 4 elements: 

Adjusted gross score,

USGA Course Rating,

USGA Slope and 113 (the Slope Rating of a course of standard difficulty)

USGA Slope Rating of the golf Course being played. 

Below is the formula for calculating a differential (round to the nearest tenth). This is a mathematical calculation that translates the score you shot to an equivalent score on a golf course of average difficulty.  This is used as the benchmark or starting point to equalize rounds played at golf courses of varying difficulty. A differentical is calculated for all scores posted.

After calculating the differentials, then select the appropriate number of differentials, and take 96% of the average (do not round – delete all numbers after the tenths digit).
HDCP Differential = (Adjusted Gross Score – USGA Course Rating) x 113
                                                            USGA Slope Rating

Number of Acceptable Scores           Differentials 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
                17                                                  Lowest 7
                18                                                  Lowest 8
                19                                                  Lowest 9
                20                                                  Lowest 10