A score of 80 on a difficult course may be a better performance than a 77 on an easier one, and it is the Score Differential calculation that allows this to be captured.
A Score Differential measures the performance of a round in relation to the relative difficulty of the course that was played, measured by the Course Rating and Slope Rating. The result of the daily Playing Conditions Calculation (PCC) is also included in the Score Differential calculation, which may provide an adjustment if course and/or weather conditions significantly impacted scores on that day.
A Score Differential is calculated using the following formula:
(113 / Slope Rating) x (Adjusted Gross Score - Course Rating - PCC adjustment)
There may be additional adjustments to the Score Differential, such as an Exceptional Score Reduction or Committee-applied adjustment. These would be clearly identified within the scoring record.
(Rule 5.1, 5.9 and 7.1a, Rules of Handicapping)