AI Caddy › Handicap › How it's calculated
How to calculate your golf handicap
The World Handicap System works your Handicap Index out in three steps: cap your score, turn it into a differential, and average your best differentials. Here's each step with the official worked examples.
In short: cap each hole at net double bogey, work out (113 ÷ slope) × (score − course rating) for each round, and average the lowest 8 of your last 20. With fewer than 20 rounds, fewer count.
Step 1: cap each hole at net double bogey
For handicap purposes no hole counts for more than net double bogey: par + 2 + the strokes you receive on that hole. (Before you have an index, the cap is par + 5.) In the rules' example, a golfer with a course handicap of 16 shot 88. Their 9 on the par-4 17th, where they receive a stroke, counts as 7, so the adjusted gross score is 86.
Step 2: turn the round into a score differential
(113 ÷ slope rating) × (adjusted gross score − course rating − PCC)
Example: an adjusted gross score of 88 on a course rated 72.0 with slope 129, on a day when the playing conditions calculation (PCC) was +1: (113 ÷ 129) × (88 − 72.0 − 1) = 13.1. The differential is rounded to one decimal, with .5 rounding up.
Step 3: average your best differentials
With 20 or more rounds in your record, your Handicap Index is the average of the lowest 8 of the most recent 20. A new golfer gets an index after 54 holes, and fewer differentials count until there are 20:
| Scores in your record | Differentials used | Adjustment |
|---|---|---|
| 3 | Lowest 1 | −2.0 |
| 4 | Lowest 1 | −1.0 |
| 5 | Lowest 1 | 0 |
| 6 | Lowest 2 (average) | −1.0 |
| 7–8 | Lowest 2 (average) | 0 |
| 9–11 | Lowest 3 (average) | 0 |
| 12–14 | Lowest 4 (average) | 0 |
| 15–16 | Lowest 5 (average) | 0 |
| 17–18 | Lowest 6 (average) | 0 |
| 19 | Lowest 7 (average) | 0 |
| 20 | Lowest 8 (average) | 0 |
Example: a new golfer's first nine scores
From the official guidance. Each row adds one differential:
| Scores | New differential | Handicap Index |
|---|---|---|
| 3 | 26.4 | 20.1 |
| 4 | 22.0 | 21.0 |
| 5 | 24.0 | 22.0 |
| 6 | 21.7 | 20.9 |
| 7 | 21.2 | 21.5 |
| 8 | 22.0 | 21.5 |
| 9 | 19.4 | 20.8 |
The first index is the lowest of three differentials, 22.1, minus 2.0. At seven scores the two lowest, 21.2 and 21.7, average 21.45, which rounds up to 21.5.
Example: a full record of 20
The lowest 8 of this golfer's 20 differentials are 10.1, 10.4, 11.0, 12.8, 13.1, 13.5, 15.6, 15.8; their average gives an index of 12.8. After one more round, an 11.8, the oldest score drops out and the index becomes 13.0.
Step 4: the safety nets
- Soft cap. If your index rises more than 3.0 above your lowest index of the past 12 months, the rise above 3.0 is halved: a Low Index of 10.0 and a calculated 14.0 gives 13.5.
- Hard cap. It can never be more than 5.0 above that low point: 10.0 can't go past 15.0.
- Exceptional scores. A differential 7.0 to 9.9 below your index takes 1.0 off it; 10.0 or more below takes 2.0 off.
From index to strokes
On the day, your index becomes a course handicap for the tees you play: Handicap Index × (slope ÷ 113) + (course rating − par). The course handicap calculator does it, and the handicap calculator runs steps 2 and 3 on your own rounds.
An unofficial estimate. Your official Handicap Index is calculated by your golf association (GHIN in the US, your national union in Great Britain and Ireland), which also applies the day's playing conditions, caps and exceptional-score reductions.