A handicap is one number that answers a hard question: how good are you, measured in a way that holds up on any course in the world?
Most golfers carry one without knowing how it’s built. That’s fine until the number does something surprising — you shoot your best round of the year and it barely moves, or you play a brutal course badly and it drops. Both make sense once you’ve seen the arithmetic. Here it is, worked from twenty real-looking rounds down to a single Handicap Index.
Step one: every round becomes a Score Differential
A raw score means nothing on its own. An 88 at your flat municipal course and an 88 at a windswept championship layout are not the same round, so the first job is to strip the course out of the number. The USGA does that with one formula:
| 113 | The Slope Rating of a course of standard difficulty. The constant everything converts to. |
| Slope Rating | How much harder the course plays for a bogey golfer than a scratch golfer. |
| Course Rating | What a scratch golfer is expected to shoot from those tees in normal conditions. |
| PCC | A daily adjustment when weather or setup clearly moved everyone’s scores. |
Run an 89 at a course rated 73.4 with a Slope of 137 through it and you get 12.9. Run a 90 at an easier course rated 69.8 with a Slope of 121 through it and you get 18.9. The higher score was the better round, and the differential is the only place that shows up.
Every acceptable round you post becomes one of these numbers, rounded to a tenth.
Step two: only your best eight count
Your Handicap Index is the average of the lowest 8 Score Differentials in your most recent 20 rounds, truncated — not rounded — to one decimal. It is a measure of what you’re capable of, not what you typically shoot. Here are twenty rounds from one golfer, with the eight that count marked in orange.
Illustrative rounds. Truncation matters: an average of 13.8375 becomes 13.8, never 13.9.
This is why a single great round barely moves the number. It replaces one differential in a rolling set of twenty and, at best, joins an average of eight. It’s also why a genuinely bad round often does nothing at all — if it isn’t in your best eight, it doesn’t touch the calculation. The system is deliberately slow to reward a fluke and slow to punish a bad day.
You don’t need twenty rounds to start. A minimum of 54 holes gets you an initial Handicap Index, in any combination of 9- and 18-hole rounds, and with fewer than twenty scores the system simply uses fewer differentials. After that it updates the day after each score is posted.
Step three: the Index becomes strokes on the tee
A Handicap Index is portable, not playable. To turn it into strokes you convert it for the specific tees you’re on, which is where the Course Handicap formula comes in: Handicap Index × (Slope ÷ 113) + (Course Rating − par). Same golfer, same 13.8, three sets of tees at a par-72 course:
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WHITE TEES
CR 69.8 · Slope 121 · Par 72
13.8 × (121 ÷ 113) = 14.8
14.8 + (69.8 − 72) = 12.6 13 strokes
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BLUE TEES
CR 71.2 · Slope 128 · Par 72
13.8 × (128 ÷ 113) = 15.6
15.6 + (71.2 − 72) = 14.8 15 strokes
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BLACK TEES
CR 73.4 · Slope 137 · Par 72
13.8 × (137 ÷ 113) = 16.7
16.7 + (73.4 − 72) = 18.1 18 strokes
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Course Handicap is rounded to a whole number for net double bogey; the unrounded value is kept to calculate a Playing Handicap.
Five strokes separate the white tees from the black for the same golfer, because a Course Handicap represents strokes needed to play to par, not to the Course Rating. That gap is real information for a Saturday morning: it’s the cost, in strokes, of moving back a set.
One more conversion sits on top. A Playing Handicap is your Course Handicap after any handicap allowance the format calls for, rounded to a whole number. In a four-ball match at 90%, that 14.8 becomes 13. Most of the time your Playing Handicap and Course Handicap are the same number, and the difference only appears in organized competition.
Why bother having one
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A fair game against anyone
Two golfers ten strokes apart can play a genuinely close match. Without handicaps, one of them already knows the result on the first tee.
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Improvement you can actually see
Scores bounce around with weather, courses, and luck. The Index filters all of that out, so when it moves, something real changed.
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Portable to every course
Your Index travels. Play a course you’ve never seen, in another state or another country, and it converts to the right number of strokes on arrival.
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Better tee-box decisions
The Course Handicap table tells you exactly what moving back costs you. Playing the right tees is the cheapest way to enjoy a round more.
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Getting an official one, and posting to it from Golfshot
Getting an official Handicap Index starts at a golf club affiliated with a state or regional golf association, through the USGA’s GHIN service. Golfshot works directly with the USGA and those associations, so the account and the app connect — and the scores you’re already keeping become the scores that maintain your Index.
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Already have a GHIN Number
1 Open Settings in Golfshot and find Handicap.
2 Enter your GHIN Number to link the account. One GHIN Number per Golfshot account.
3 Score your round hole by hole and save it. Golfshot posts it to GHIN.
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Need one for the first time
1 Golfshot sends you to the USGA at getahandicap.usga.org.
2 The USGA handles the club match and the payment. Price varies by the association your club sits under.
3 Link the new GHIN Number in Golfshot, post 54 holes, and your Index appears.
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Golfshot is the golf GPS app that works directly with the USGA and state and regional golf associations for integrated Handicap Index score posting and new GHIN Account purchases. In practice that means one scorecard: the round you play for yardages and stats is the round that maintains your handicap.
More than 186,000 Golfshot golfers are already carrying a handicap figure in the app. If you’re one of the ones tracking it by hand, linking a GHIN Number is the step that makes it official.
Sources: USGA Rules of Handicapping and World Handicap System FAQs, usga.org, accessed August 2026 (Score Differential and Course Handicap formulas, Rules 4.5, 5.1, 6.1, 6.2, 7.1a); golfshot.com blog and Golfshot Support Center on GHIN linking and net double bogey posting. Handicap Index®, Course Handicap™, Playing Handicap™, Course Rating™, Slope Rating™ and GHIN® are marks of the USGA. Worked example figures are illustrative.