Score Differential (How a Handicap Index Is Calculated)
Also known as: score differential, handicap differential, how is my handicap calculated, how a handicap is calculated, handicap calculation, handicap formula, best 8 of 20, calculate my handicap
A Score Differential rates one round against the difficulty of the tees you played. The formula is (113 divided by the Slope Rating) times (adjusted gross score minus Course Rating minus any playing conditions adjustment). Your Handicap Index is the average of your lowest 8 differentials from your most recent 20, rounded to one decimal.
Each acceptable score becomes a Score Differential. First your gross score is capped hole by hole to give the adjusted gross score. Once you have an index, the cap is net double bogey. Then the Course Rating is subtracted, along with any adjustment from the day's playing conditions calculation (PCC). The result is scaled by 113 divided by the Slope Rating. A Slope Rating of 113 marks a course of standard difficulty. Nine-hole scores are turned into an 18-hole value.
Say you post an adjusted 90 from tees rated 70.5 with a Slope Rating of 125, and the PCC is zero. 90 minus 70.5 is 19.5. 113 divided by 125 is 0.904. 19.5 times 0.904 gives a differential of about 17.6. Your Handicap Index is the average of the lowest 8 of your most recent 20 differentials, rounded to the nearest tenth. With fewer than 20 scores, a table in Rule 5.2a sets how many count and whether an adjustment applies.
Safeguards shape the result. A soft cap slows any rise of more than 3.0 above your lowest index of the past year. A hard cap stops the rise at 5.0. A differential at least 7.0 better than your index counts as an exceptional score and triggers an extra reduction. Your index should update no later than the day after you post.
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You do not need to do the math. Post hole-by-hole scores and the system applies the caps and the formula for you.
Watch which differentials are in your best 8 and when they drop out of the last 20. That tells you whether your index is likely to rise or fall soon.
Example
A golfer posts an adjusted 92 at a course rated 71.2 with a Slope Rating of 128 and no PCC adjustment. Her differential is 113 divided by 128, times 92 minus 71.2, about 18.4. It joins her record, and her index becomes the average of her best 8 of the last 20.
Why it matters
The formula shows why tough courses and bad weather do not ruin your index. It also shows why only your better rounds count toward it.
Common mistakes
- Thinking your index is the average of all your scores
- Forgetting to cap bad holes at net double bogey before calculating
- Assuming a tough course always raises your index
- Expecting one great round to drop your index by the full difference
Frequently asked questions
How is my golf handicap calculated?
Each round becomes a Score Differential: 113 divided by the Slope Rating, times your adjusted gross score minus the Course Rating and any PCC adjustment. Your Handicap Index is the average of your lowest 8 of your last 20 differentials.
What is a score differential in golf?
It is the number a round contributes to your handicap. It compares your adjusted gross score with the Course Rating and scales it by the Slope Rating. This lets rounds on different courses compare fairly.
Why didn't my handicap go down after a good round?
Only your lowest 8 of your last 20 differentials count. A good round lowers your index only if it beats one of those 8. The old score dropping out of the last 20 also matters.
How many scores count toward my handicap?
Your lowest 8 Score Differentials from your most recent 20 count. With fewer than 20 scores, the Rules of Handicapping use a table to decide how many count.
Sources
Related terms
- Handicap IndexA Handicap Index is the World Handicap System (WHS) measure of a golfer's demonstrated playing ability on a neutral course. A lower index means a better player.
- Getting a Golf HandicapTo get a handicap, join a golf club or golf association authorized to issue a World Handicap System Handicap Index, then post your scores. Your national association sets how many holes you need, up to 54. In the USGA system it is 54 holes from any mix of 9- and 18-hole rounds.
- Course Rating vs Slope RatingCourse rating estimates the score a scratch golfer would shoot on a course. Slope rating measures how much harder that same course plays for a bogey golfer relative to a scratch golfer. Together they adjust a handicap for the specific course being played.
- Net Double Bogey (Maximum Hole Score)Net double bogey is the most you can count on any hole for handicap purposes once you have an index. It equals par plus 2 plus any strokes you receive on that hole. Before you have an index, the cap is par plus 5.
- Course Handicap vs Handicap IndexHandicap Index is a portable number representing a golfer's general ability, calculated from past scores. Course handicap converts that same index into the actual number of strokes they receive on a specific course and tee, using that course's slope rating.
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