An 18hole Score Differential is calculated as follows and rounded to the nearest tenth, with .5 rounded upwards:
Note: The PCC adjustment ranges from 1.0 to +3.0 (see Rule 5.6 Playing Conditions Calculation). 
If a player submits a 9hole score, an 18hole Score Differential must be created by combining two 9hole Score Differentials. A 9hole Score Differential is calculated as follows using 50% of the playing conditions calculation (PCC) adjustment for the day: 
Notes:

An 18hole Score Differential is then created by either:
Note: An uncombined 9hole score will be discarded when it becomes older than the twentieth Score Differential in the scoring record.
When an adjusted gross score calculates lower than the Course Rating, this results in the Score Differential being a negative number. Where this occurs, rounding is made upward towards 0. For example: