Golf ScoutWhat is a score differential?
A score differential is one round's score, adjusted for how hard the course was: 113 ÷ slope rating × (adjusted gross score − course rating − PCC). It's roughly the handicap you played to that day. Your Handicap Index is the average of your best 8 differentials from your last 20 rounds.
The formula
Score differential = 113 ÷ slope rating × (adjusted gross score − course rating − PCC)
It answers one question: how well did you play, given how hard the course played? England Golf puts it as the number that tells you how well you played relative to the difficulty. Each part does a job:
- Adjusted gross score. Your score with any hole over net double bogey brought down to it, so one blow-up hole doesn't distort the round.
- Course rating. What a scratch golfer is expected to shoot from those tees. Taking it away gives how many strokes you were above scratch standard.
- 113 ÷ slope rating. Scales those strokes to a course of standard difficulty. On a high-slope course, being well over the rating is expected, so it counts for less. See course rating and slope explained.
- PCC, the playing conditions calculation. If scores across the whole field that day were far higher or lower than expected, because of a gale or a soaked course for example, an adjustment of −1 to +3 is applied. Most days it's 0, and it's 0 whenever fewer than eight acceptable scores were submitted.
Worked example
You shoot an adjusted 90 off tees rated 71.2 with a slope of 128.
- 90 − 71.2 = 18.8 strokes above the rating.
- 113 ÷ 128 × 18.8 = 16.6.
If it was a filthy day and the PCC came out at +2, the sum becomes 113 ÷ 128 × (90 − 71.2 − 2) = 14.8: the conditions are taken into account, so your round counts for more.
The same score on different courses
This is why differentials exist. A 90 is a very different round depending on where you played it:
| Tees | Rating | Slope | Differential for a 90 |
|---|---|---|---|
| Gentle parkland, par 70 | 68.4 | 112 | 21.8 |
| Average club course, par 72 | 71.2 | 128 | 16.6 |
| Championship tees, par 72 | 74.5 | 140 | 12.5 |
Example ratings. Each course's real figures are on its scorecard.
From differentials to your Handicap Index
Your Handicap Index is the average of the lowest 8 differentials in your last 20 scores, rounded to one decimal place. Fewer count while you have fewer than 20 scores; our guides to working out your handicap and how many rounds you need have the details.
Because only your best 8 count, your index describes your better days, not your average. England Golf's iGolf says golfers are only expected to play to their handicap once every four or five rounds. So most of your differentials will be above your index, and that's normal.
What's a good differential?
Compare it with your Handicap Index on the day:
- Close to your index or lower: a good round, likely to be one of your counting 8.
- A few strokes above: an ordinary round.
- 7.0 or more below your index: an exceptional score. Your index is cut by a further 1.0, or by 2.0 if the differential was 10.0 or more below.
Whether a new differential lowers your index also depends on the one leaving your record. That's covered in why your handicap can go up after a good round.
9-hole differentials
A 9-hole round gets a 9-hole differential from the 9-hole rating and slope, and the system then adds an expected differential for the other nine to make an 18-hole one. See 9-hole handicap scores.
Work yours out
Put your adjusted score, the course rating and the slope into the handicap calculator for each round. It gives the differential for each, and an estimate of your Handicap Index once you've entered three or more.
Related guides
- Do 9-hole scores count for your handicap?
- How to score with a handicap: net and Stableford
- How many rounds do you need for a handicap?
Sources
Golf Scout works out a differential for each rated round and a handicap estimate from them. Get Golf Scout on the App Store, free for iPhone and Apple Watch.