Computing Index
By Differentials
A handicap differential is the difference between the adjusted gross score and the NCGA/USGA Course Rating, multiplying the difference by 113, dividing the results figure by the NCGA/USGA Slope Rating and rounding off to the nearest tenth. The following is an example for a course with a 71.5 Course Rating and a 130 Slope Rating.
| Adjusted Gross Score | 95 |
| Course Rating | 71.5 |
| Difference | 23.5 |
| Handicap Differential | 113 x 23.5 divided by 130 = 20.4 |
The value 113 in the above formula is the national standard for Slope Ratings and is used to weigh differentials.
INDEX Formula
Lowest 10 of Last 20 Differentials. The INDEX is computed from the lowest 10 of the player’s last 20 rounds as follows:
| Total of 10 lowest differentials | 147.9 |
| Total averaged | 14.79 |
| Total multiplied by 96% | 14.19 |
| Delete all numbers after the tenths digit | 14.1 |
| NCGA/USGA index is | 14.1 |
If you have fewer than 20 differentials available:
| Available | Used |
|---|---|
| 1-4 | No INDEX issued |
| 5 or 6 | Lowest 1 |
| 7 or 8 | Lowest 2 |
| 9 or 10 | Lowest 3 |
| 11 or 12 | Lowest 4 |
| 13 or 14 | Lowest 5 |
| 15 or 16 | Lowest 6 |
| 17 | Lowest 7 |
| 18 | Lowest 8 |
| 19 | Lowest 9 |
