Quick Answer — How a Golf Handicap Index Is Calculated
Under the USGA World Handicap System (WHS), every acceptable round produces a Score Differential: Score Differential = 113/(Slope Rating) × (Adjusted Gross Score - Course Rating - PCC). PCC is a daily Playing Conditions Calculation adjustment applied by official handicap services based on how an entire field of golfers scored that day — this calculator treats it as 0, since it requires field-wide data no offline tool has access to.
Your Handicap Index is not a simple average of every differential you've posted. It's the average of your *lowest* differentials — how many depends on how many rounds are in your scoring record — plus a small adjustment for very new golfers, multiplied by 0.96, then truncated (not rounded) to one decimal place.
Once you have a Handicap Index, a Course Handicap converts it to the actual strokes you receive on a specific course and tee: Course Handicap = Handicap Index × (Slope Rating)/113 + (Course Rating - Par).