World Handicap System Rules
This app implements the World Handicap System (WHS) rules effective January 2024. Here's how your handicap index is calculated and what each component means.
Score Differential
Every round produces a score differential — a measure of how you played relative to the course difficulty:
A lower differential means a better round. The course rating represents the expected score for a scratch golfer, and the slope rating (55–155, standard 113) measures how much harder the course plays for a bogey golfer compared to a scratch golfer.
Handicap Index Calculation
Your handicap index is based on your best recent differentials, not all of them. The number of differentials used follows a sliding scale:
| Rounds Available | Differentials Used | Adjustment |
|---|---|---|
| 3 | Lowest 1 | −2.0 |
| 4 | Lowest 1 | −1.0 |
| 5 | Lowest 1 | None |
| 6 | Lowest 2 | −1.0 |
| 7–8 | Lowest 2 | None |
| 9–11 | Lowest 3 | None |
| 12–14 | Lowest 4 | None |
| 15–16 | Lowest 5 | None |
| 17–18 | Lowest 6 | None |
| 19 | Lowest 7 | None |
| 20 | Lowest 8 | None |
The selected differentials are averaged, the adjustment (if any) is applied, and the result is multiplied by 0.96 to produce the handicap index.
With fewer than 3 rounds on record, a provisional index of 54.0 (the maximum) is used.
Equitable Stroke Control (ESC)
Before calculating a differential, each hole score is capped at net double bogey:
For example, on a par 4 where you receive one handicap stroke, the maximum score used for handicap purposes is 7 (4 + 2 + 1). Your actual score is preserved — only the adjusted score is used in the differential calculation.
When you enter hole-by-hole scores, the app applies ESC automatically and shows both the actual and adjusted totals when they differ.
Soft Cap & Hard Cap
Your Low Handicap Index (Low HI) is the lowest index you've held in the past 12 months. Two caps prevent your index from rising too far above it:
| Condition | Effect |
|---|---|
| Index exceeds Low HI by more than 3.0 | Soft cap: 50% of the excess above 3.0 is removed |
| Index exceeds Low HI by more than 5.0 | Hard cap: index is capped at Low HI + 5.0 |
For example, if your Low HI is 12.0 and your calculated index is 18.5, the soft cap applies first (excess above 15.0 is halved), then the hard cap limits the result to 17.0.
Exceptional Score Reduction
When you post an exceptionally good round — a differential far below your current index — an additional reduction is applied to all 20 of your most recent differentials:
| Gap Below Index | Reduction Applied |
|---|---|
| 7.0 to 9.9 strokes | −1.0 to each differential |
| 10.0 or more strokes | −2.0 to each differential |
This accelerates the index drop after a breakthrough round. The reduction fades naturally as the adjusted rounds age out of your 20-round window.
9-Hole Rounds
You can record front 9 or back 9 rounds. The differential is calculated using the nine-hole course rating and slope for the nine you played. An expected differential for the unplayed nine is added:
If the course has specific front/back 9-hole ratings and slopes, those are used. Otherwise, the app falls back to half the 18-hole course rating with the full slope.
Course Handicap
Your course handicap — the number of strokes you receive on a specific course — is calculated as:
This adjusts your index for the difficulty of the specific tees you're playing. The result is rounded to the nearest whole number.