Golf handicap calculator (World Handicap System)

Each round becomes a score differential, (113 ÷ Slope Rating) × (adjusted gross score − Course Rating − PCC). The Handicap Index is the average of the lowest 8 of the most recent 20 differentials, rounded to the nearest tenth (Rules of Handicapping, Rule 5.2b). A score of 88 on a course rated 71.8 with a slope of 131 gives (113 ÷ 131) × 16.2 = 14.0.

Scores from at least 54 holes, such as three 18-hole rounds (Rule 4.5). With 3 differentials the index is the lowest one minus 2.0; with 4 it is the lowest minus 1.0; with 5 the lowest; with 6 the average of the lowest 2 minus 1.0. The count used then rises to the lowest 8 of 20. The Rules' own example turns differentials of 15.3, 15.2 and 16.6 into an initial index of 13.2.

The Handicap Index measures ability on a course of standard difficulty, Slope Rating 113. The course handicap is the number of strokes you get on a particular set of tees: Handicap Index × (Slope ÷ 113) + (Course Rating − par), rounded to a whole number with .5 rounded up (Rule 6.1). A 12.2 index on tees rated 71.8, slope 131, par 72 plays to 14.

Net double bogey: par plus 2 plus any handicap strokes you receive on the hole (Rule 3.1b). A player getting one stroke on a par 4 can post no more than 7 there. Until you have a Handicap Index, the limit is par plus 5 (Rule 3.1a). The adjusted gross score is the total after these caps, and it is the figure that goes into the differential.

They limit how fast a Handicap Index can rise (Rule 5.8). If a new index is more than 3.0 above your Low Handicap Index from the previous 365 days, only half of the increase beyond 3.0 counts, and the total rise can never exceed 5.0. With a Low Handicap Index of 8.6 and a calculated 12.2, the soft cap gives 8.6 + 3.0 + 0.3 = 11.9.

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 8 worked examples whose answers come from independent sources; for example, “20 rounds on three courses” is checked against Python decimal: 20 differentials rounded per Rule 5.1 (89 on 70.4/124 gives 16.95, rounded up to 17.0); lowest 8 average 12.2125 → 12.2; 12.2 × 131/113 − 0.2 = 13.9434 → 14; × 0.95 = 13.25 → 13.

USGA and R&A — Rules of Handicapping, effective 2024 (Rules 3.1, 4.5, 5.1–5.3, 5.8, 6.1, 6.2, Appendix C); R&A — Rules of Handicapping, Rule 5: Handicap Index calculation; USGA — What exactly are Course Rating and Slope Rating? (slope 55 to 155, standard 113).