Understanding the USGA handicap as applied to Duffers League

1. There are 3 key terms to observe in the following explanation.

   Handicap Differential	—	This is a number that is calculated after each round.  It’s supposed to represent how well you just played if you had played on some mythical standard course.
   Handicap Index	—	This is a number that is supposed to reflect how you would typically play on some mythical standard course.
   Course Handicap	—	This is the number you would use on your golf card.

2. A Handicap Differential value is computed for each round as:

   Hdcp Diff	=	(AdjGrossScore − USGA CourseRating) x 113	(rounded to nearest tenth)
   		USGA SlopeRating

   where:

   AdjGrossScore	=	Total score after modifying blow-up holes — see (6c) below
   USGA_CourseRating	=	An assigned number to a particular golf course
   USGA_SlopeRating	=	An assigned number to a particular golf course

3. Only your best Handicap Differentials are used to calculate your Handicap Index and it depends on how many rounds you have recorded.

   USGA Rules
   # of Rounds	# of Handicap Differentials to use
   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 or more	Lowest 10

   NOTE:  As far as the USGA is concerned, you can’t even get a handicap until you log at least 5 scores.  For Duffers League, we will use the following rules.

   Duffers League Rules
   # of Rounds	# of Handicap Differentials to use
   1	Recursively determine handicap until net score does not change
   2 or more	Lowest 4 of most recent 5

4. The Handicap Index is then calculated as:
   1. Find the average of the Handicap Differentials to be used.
   2. Multiply by 0.96.
   3. Delete all numbers after the tenths’ digit (do not round).
   4. This is your Handicap Index.  It’s like your AMEX card — take it everywhere you want to golf.  It’s not your handicap but it is what the golf course needs to compute your handicap for that particular course.
5. The Course Handicap is calculated as:

   Hdcp	=	HandicapIndex x USGA_ SlopeRating	(rounded to nearest integer)
   		113

6. Since the Duffers League is a 9-Hole league, there are some additional points the USGA calls out:
   1. You can simply double your Handicap Index to obtain a valid 18 hole round handicap index.
   2. The front 9 of a course will likely have a different Slope and Rating as the back 9.  Thus, you can have a different handicap for each side.  At Pine View, it looks like this:

      Hemlock	Front 9	Back 9	Total 18
      Course Rating	34.1	34.2	68.3
      Slope Rating	111	111	111

      Spruce	Front 9	Back 9	Total 18
      Course Rating	35.0	35.0	70.0
      Slope Rating	119	119	119

   3. To keep the sand-baggers in-line, the rule of Equitable Stroke Control (ESC) applies.  It states, for a calculated 9-Hole course handicap, you are not allowed to put down an abnormally high hole score.  The lower the handicap, the lower the ceiling as follows:

      9-Hole Course Hdcp	Max Hole Score
      ≤ 4	Double Bogey
      5 to 9	7
      10 to 14	8
      15 to 19	9
      ≥ 20	10

      NOTE:  For the Duffers League, do NOT alter your card during play for stroke control.  Points are determined by what your actual hole and total scores are.  The ESC is applied for calculating your Handicap Differentials.

7. Final Points:
   1. The USGA handicap system has a lot of stuff about tournament scores that can impact your Handicap Differential/Index.  Duffers League does not apply these rules.
   2. For the Duffers League, there is no maximum allowed Handicap Index.