This is an example of how handicaps are calculated using the USGA Handicap System.  Here are the results of Sam’s Last 20 Scores as of 5/15/09. 

First look at the data from the Last 20 Scores web page.

It shows that Sam’s Index, after playing the Dales on the 15^th, was 16.0. The Diff (Handicap Differential) for each score was calculated using the USGA formula Diff = (Score - Rating) x 113/Slope. This data was sorted by the Diff column.

According to the USGA handicap method the Index is calculated using the 10 lowest Diff values. The 10 scores with the highest Diff values were deleted.

To calculate the Index, the 10 lowest Diff values were averaged (16.73) and that value was multiplied by 96% to get 16.061. Again according to the USGA all digits beyond the tenths place are dropped this gives 16.0 as the Index, as of 5/15. The HCP depends on the course that is played; on tougher courses you get a higher HCP. The handicaps at Dales and Eagle have been calculated; there is a 4 pin difference in the handicaps.

When Sam next plays, the score from WGC Xenia will be dropped, his new score will be added, and the process to find the Index and HCP will begin anew.  In the years before 2009, the software that was used to calculate the handicaps always used the slope of the Hills course.  According to the USGA this was incorrect because the handicaps did not reflect the difficulty of the course.