The World Handicap System, WHS for short, has been in use around the world since 2020 and 2021. It calculates differently from many older systems: your Handicap Index is not nudged up or down after every round but is an average of your best results. That sounds complicated, but four formulas explain it.
Here is how the WHS calculates, step by step, with a real example from the DeepSwing golf course GPS.
The terms
| Term | What it is |
|---|---|
| Course Rating (CR) | how many strokes a scratch golfer needs on this course from this tee |
| Slope Rating | how much harder the course is for an average golfer; 113 is the standard |
| Score differential | the result of a round, converted to a standard course |
| Handicap Index | your handicap, the average of your best differentials |
| Course handicap | your strokes for a specific course and tee |
| Playing handicap | the course handicap adjusted for the format |
Step 1: the score differential of a round
Every round is converted into a score differential:
Score differential = (113 ÷ Slope) × (adjusted gross score − Course Rating − PCC)
The adjusted gross score is your stroke total in which no hole counts worse than a net double bogey: par plus two plus the handicap strokes you receive on that hole. PCC is a daily value for unusually hard or easy conditions, usually zero.
Example from the app: 81 strokes at Münchner Golfplatz Eschenried from the yellow tee, Course Rating 71.5, Slope 128.
(113 ÷ 128) × (81 − 71.5) = 0.883 × 9.5 = 8.4
Step 2: the Handicap Index
The Handicap Index is the average of the best 8 of your last 20 score differentials. If you have fewer than 20 rounds, a sliding scale applies:
| Rounds | counted | adjustment |
|---|---|---|
| 3 | best 1 | −2.0 |
| 4 | best 1 | −1.0 |
| 5 | best 1 | 0 |
| 6 | best 2 | −1.0 |
| 7–8 | best 2 | 0 |
| 9–11 | best 3 | 0 |
| 12–14 | best 4 | 0 |
| 15–16 | best 5 | 0 |
| 17–18 | best 6 | 0 |
| 19 | best 7 | 0 |
| 20 | best 8 | 0 |
In the app's example there are five rounds with differentials of 8.4, 10.2, 12.8, 11.0 and 15.4. With five rounds the best differential counts without adjustment, so the Handicap Index is 8.4. The app marks the differential that counts.
The index is capped at 54.0. To stop it running away after a poor spell there is a brake: if it rises more than 3.0 above your lowest index of the past twelve months, the increase beyond that only counts half, and it can't go more than 5.0 above it. The other way round, an exceptionally good round, at least 7.0 below your current index, earns an extra reduction.
Step 3: the course handicap
The Handicap Index applies to a standard course. For your course and tee it is converted:
Course handicap = Handicap Index × (Slope ÷ 113) + (Course Rating − Par)
In the example: 8.4 × (128 ÷ 113) + (71.5 − 72) = 9.52 − 0.5 = 9.02, rounded to 9. On this course you receive nine strokes.
Step 4: the playing handicap
Depending on the format, the course handicap is multiplied by a percentage, the handicap allowance. Which percentage applies is set by the committee for each competition. At 100 percent the playing handicap equals the course handicap, so 9 in the example as well.
What the app calculates and what it doesn't
DeepSwing calculates the Handicap Index under the WHS from the rounds you play in the app and shows the course handicap and playing handicap for the last tee you played. With "Use for the playing handicap" you carry the value over to your next round.
Important: this is our own calculation from your app rounds. Your official handicap is kept by your club and national association, and only that counts for competitions.
Frequently asked questions
How is the Handicap Index calculated?
As the average of the best 8 of your last 20 score differentials. With fewer rounds, fewer results count, some with a downward adjustment.
What is the difference between Handicap Index and course handicap?
The index applies to a standard course with a slope of 113. The course handicap converts it to a specific course and tee using slope, Course Rating and par.
What does a slope of 113 mean?
113 is the standard value for a course of average difficulty. If the slope is higher, you receive more strokes on that course.
Is the handicap from the app official?
No. The app applies the WHS formulas to your app rounds. Your official handicap is kept by your club.
Scorecard and handicap on the course: the DeepSwing golf course GPS, free on iPhone.