Quick answer: A score of 85 on a course rated 72.1 with slope 125 gives a differential of (113 ÷ 125) × (85 − 72.1) = 11.7; your Handicap Index is the average of your 8 lowest differentials from the last 20 rounds.
How it's calculated
Score differential = (113 ÷ slope rating) × (adjusted gross score − course rating − PCC), rounded to one decimal. 113 is the slope of a course of standard difficulty; PCC (playing conditions calculation) is the daily adjustment from −1 to +3 your club or federation applies, usually 0.
Handicap Index = the average of the lowest 8 differentials among your most recent 20, rounded to one decimal, with a maximum of 54.0. With fewer than 20 rounds, the WHS table uses fewer differentials: the lowest 1 for 3–5 scores (minus 2.0 for 3 scores, minus 1.0 for 4), the lowest 2 for 6–8 (minus 1.0 for 6), 3 for 9–11, 4 for 12–14, 5 for 15–16, 6 for 17–18 and 7 for 19.
Use the adjusted gross score, where each hole is capped at net double bogey. Your federation's official index can also include the soft and hard caps and exceptional-score reductions, which need your full scoring history.
Worked examples
- 85, course rating 72.1, slope 125: (113 ÷ 125) × 12.9 = 11.7
- 88, course rating 72.1, slope 128: (113 ÷ 128) × 15.9 = 14.0
- The 20 sample rounds, lowest 8: (10.5 + 11.4 + 11.8 + 12.3 + 13.6 + 14.0 + 14.6 + 14.9) ÷ 8 = 12.9
Differentials used with fewer than 20 scores (WHS rule 5.2a)
| Scores | Lowest used | Adjustment |
|---|---|---|
| 3 | 1 | −2.0 |
| 4 | 1 | −1.0 |
| 5 | 1 | 0 |
| 6 | 2 | −1.0 |
| 7–8 | 2 | 0 |
| 9–11 | 3 | 0 |
| 12–14 | 4 | 0 |
| 15–16 | 5 | 0 |
| 17–18 | 6 | 0 |
| 19 | 7 | 0 |
| 20 | 8 | 0 |
Frequently asked questions
Where do I find the course rating and slope?
On the scorecard or the course's page in your federation's app, for the tees you played. Men's and women's ratings differ.
What is the highest Handicap Index?
54.0 under the World Handicap System.
Is my Handicap Index the same as my course handicap?
No. Your course handicap for a round is your index × slope ÷ 113 + (course rating − par), so it changes from course to course.
How many rounds do I need for a Handicap Index?
Under the World Handicap System, 54 holes is enough for a first index, so three 18-hole rounds will do. It settles down once you've got 20 scores in.
What is net double bogey?
The most a hole can count for your handicap: par, plus 2, plus any strokes you get on that hole. A worse score on the hole is cut back to it.
Why didn't my index change after a good round?
Only your best 8 of the last 20 count. A new round moves the index only if it makes that top 8, or if the old round it pushes out was one of them.