Handicap Index calculator

Under the World Handicap System, used in the United States since 2020, your Handicap Index is worked out from your score record in three steps (Rule 5.2 of the Rules of Handicapping):

1. Turn each score into a score differential, a measure of how you played against the difficulty of that tee.
2. Take the lowest differentials from your 20 most recent scores: the lowest 8 when you have 20, fewer when you have fewer (see the Rule 5.2a table below).
3. Average them, add the Rule 5.2a adjustment if there is one, and round to the nearest tenth with a half rounding up. The result is capped at 54.0.

Handicap Index = average of the lowest differentials + adjustment, rounded to one decimal place. There is no longer a 0.96 multiplier: the old USGA formula took 96% of the average as a bonus for excellence, and the World Handicap System dropped it.

The calculator above opens on eight scores. With 8 scores, the lowest 2 differentials count: 13.3 and 13.6 average to 13.45, which rounds up to a Handicap Index of 13.5.

A score differential converts a score into strokes above the Course Rating on a course of standard difficulty (Rule 5.1a): score differential = (113 ÷ Slope Rating) × (adjusted gross score minus Course Rating minus PCC), rounded to the nearest tenth with a half rounding up. A Slope Rating of 113 is standard, so on a harder tee the same number of strokes over the rating counts for less.

PCC is the playing conditions calculation. GHIN works it out each day from the scores posted at a course and sets it from -1 to +3 when conditions made scoring easier or harder than normal; on most days it is 0. Had the PCC been +1 that day, the same 88 would give (88 minus 71.4 minus 1) × 113 ÷ 128 = 13.77, a differential of 13.8.

A score below the Course Rating gives a minus differential. A half then rounds up toward zero (Rule 5.1c): -1.55 becomes -1.5, while -1.56 becomes -1.6.

Until you have 20 scores, Rule 5.2a sets how many of your lowest differentials count, and with 3, 4 or 6 scores it takes a little off the result. You need scores from at least 54 holes for an index, which is three 18-hole scores.

For example, a new golfer with three 18-hole scores and differentials of 10.0, 12.0 and 14.0 takes the lowest, 10.0, and subtracts 2.0 for a first Handicap Index of 8.0.

The score you enter is your adjusted gross score: your total after each hole is capped for handicap purposes, so one blow-up hole does not inflate your index. Once you have a Handicap Index, the most you count on any hole is a net double bogey: par, plus 2, plus any handicap strokes you receive on that hole (Rule 3.1b).

• With a course handicap of 15 you receive a stroke on the holes with stroke index 1 to 15. On a par 4 with stroke index 10, your maximum is 4 + 2 + 1 = 7.
• On a par 3 with stroke index 16, the same player receives no stroke, so the maximum is 3 + 2 = 5.
• With a course handicap of 22 you receive two strokes on the holes with stroke index 1 to 4. On a par 5 with stroke index 2, your maximum is 5 + 2 + 2 = 9.
• Before you have a Handicap Index, the maximum on each hole is par plus 5.

Net double bogey needs your course handicap for the tee you played, which you can work out with the course handicap calculator. When you post hole by hole, GHIN applies the adjustment for you.

Two more rules can change an index, and this calculator does not apply either, because both depend on your full scoring history.

Soft cap and hard cap (Rule 5.8). Once you have 20 scores, your Low Handicap Index is the lowest index you held in the 365 days before your most recent score. If a newly calculated index is more than 3.0 above it, only half of the increase beyond 3.0 counts (the soft cap), and the index can never be more than 5.0 above it (the hard cap). With a Low Handicap Index of 10.0, a calculated 14.0 becomes 13.5, and a calculated 18.0 becomes 15.0.

Exceptional score reduction (Rule 5.9). A score differential 7.0 to 9.9 strokes below the Handicap Index you played off takes 1.0 off each of your 20 most recent differentials, and one 10.0 or more below takes 2.0 off. A golfer with three differentials of 20.0, 22.0 and 24.0 has an index of 18.0. A fourth score with a differential of 10.5 is 7.5 below it. Four scores count the lowest differential minus 1.0, which would be 10.5 minus 1.0 = 9.5, but the reduction first takes 1.0 off every differential, so the new index is 9.5 minus 1.0 = 8.5.

• Nine-hole scores. GHIN combines a nine-hole score with the score you would be expected to make on the other nine, based on your index, to make an 18-hole differential (Rule 5.1b). This calculator takes 18-hole scores only.
• Net double bogey. When you post hole by hole, GHIN caps each hole for you. Here you enter a total that is already adjusted.
• PCC. GHIN works out the playing conditions calculation from the day's scores. Here you type it in, and 0 is right on most days.
• Caps and exceptional scores. GHIN applies the soft and hard caps and exceptional score reduction from your full record.
• Your record. GHIN keeps your 20 most recent scores and revises your index daily. This calculator uses the scores you enter as that record.

Link your GHIN account and Wedge imports your Handicap Index, works out your course handicap on every tee, and when you finish you can post your round to GHIN hole by hole from the app, so GHIN applies net double bogey and the rest of the rules. Your official index then comes back from GHIN.

Without a GHIN link, Wedge works out an index from your finished Wedge rounds once you have 54 holes, with the same Rule 5.2a table, nine-hole scores combined with an expected score, and exceptional score reduction. It is labelled Calculated by Wedge and is not an official Handicap Index. It counts your hole scores as played, without the net double bogey adjustment or the caps, so it can sit a little higher than the index GHIN would give you.