text: A score differential is calculated from each of the scores after any net double bogey adjustments (an adjustment which allows for a maximum number of strokes per hole based on the player's course handicap) have been applied, using the following formula:
  Only 18-hole differentials are used for the calculation of a handicap index. As such, 9-hole differentials need to be combined before being used, subject to remaining one of the 20 most recent differentials. The system also allows for situations where less than 18 (or 9) hole have been played, subject to a minimum of 14 (or 7) holes having been completed, by "scaling up" with net pars for any missing holes.
  The score differentials are rounded to one decimal place, and the best 8 from the last 20 submitted scores are then averaged and rounded to one decimal place to produce the handicap index. Initial handicaps are calculated from a minimum of five scores using adjustments that limit each hole score to a maximum of . If there are at least 5 but fewer than 20 qualifying scores available, the handicap index is calculated using a set number or differentials according to how many scores are available, with an additional adjustment made to that average in some circumstances.
  The basic formula for calculating the handicap index is as follows (where  is the number of differentials to use), with the result rounded to one decimal place: