How the World Handicap System calculates your index
Every acceptable 18-hole round becomes a Score Differential: Score Differential = (113 ÷ Slope Rating) × (adjusted gross score − Course Rating − PCC). The result is rounded to the nearest tenth, with .5 rounded up. PCC, the playing conditions calculation, is usually 0 and ranges from −1 to +3 on days when scoring was unusually easy or hard.
With 20 or more rounds on record, your Handicap Index is the average of the lowest 8 of your most recent 20 differentials, rounded to the nearest tenth. Unlike the old USGA formula there is no 0.96 multiplier. The maximum Handicap Index is 54.0.
With fewer than 20 rounds, the Rules of Handicapping (Rule 5.2a) use fewer differentials and, for very short records, subtract a small adjustment:
| Differentials in record | Lowest used | Adjustment |
|---|---|---|
| 3 | 1 | −2.0 |
| 4 | 1 | −1.0 |
| 5 | 1 | 0 |
| 6 | 2 (average) | −1.0 |
| 7 or 8 | 2 | 0 |
| 9 to 11 | 3 | 0 |
| 12 to 14 | 4 | 0 |
| 15 or 16 | 5 | 0 |
| 17 or 18 | 6 | 0 |
| 19 | 7 | 0 |
| 20 | 8 | 0 |
Worked example
A round of 92 on a course with Course Rating 71.2 and Slope Rating 128 gives (113 ÷ 128) × (92 − 71.2 − 0) = 18.36, which rounds to 18.4.
The six sample rounds preloaded in the calculator produce differentials of 18.4, 16.0, 18.9, 16.6, 15.3 and 18.0. With six differentials the rule uses the average of the lowest two, (15.3 + 16.0) ÷ 2 = 15.65, then subtracts 1.0, so the Handicap Index is 14.65, rounded to 14.7.
Course Handicap = Handicap Index × (Slope Rating ÷ 113) + (Course Rating − par). An index of 14.3 on tees rated 71.2 / 128 with par 72 gives 14.3 × 1.1327 − 0.8 = 15.40, so you receive 15 strokes.
What this estimate leaves out
Your official index comes from your golf club or national association and follows every part of the rules. Adjusted gross score already includes the net double bogey limit on each hole, which needs your Course Handicap and the stroke index of every hole. The official calculation also applies exceptional-score reductions and the soft and hard caps that limit how fast an index can rise against your low index of the past year.
The rules cited here are the Rules of Handicapping effective January 2024, issued jointly by the USGA and The R&A. Nine-hole scores are combined with an expected score under those rules, which this calculator does not model; enter 18-hole scores only.