How to Calculate a Score Differential

A score differential is your round's Adjusted Gross Score measured against the Course Rating and scaled by the Slope Rating. The USGA formula is (113 / Slope Rating) x (Adjusted Gross Score - Course Rating - PCC adjustment), rounded to the nearest tenth. Use the score differential calculator or the golf handicap calculator to do the sum for you.

That's the per-round number. Your Handicap Index is built from a batch of them. Here's how it all fits.

How to calculate a score differential in 5 steps

Find the Course Rating and Slope Rating for the tees you played. They're on the card or the course's rating info.
Work out your Adjusted Gross Score. Cap any blow-up hole at net double bogey.
Apply the formula. (113 / Slope Rating) x (Adjusted Gross Score - Course Rating - PCC adjustment).
Round it the way the rules say. Nearest tenth, with .5 rounded up.
See how it feeds your Index. Your Handicap Index averages your lowest differentials from your most recent 20.

Step 1: Course Rating and Slope Rating

Two numbers per set of tees. The Rules of Handicapping define them like this:

Term	Official definition (Rules of Handicapping)
Course Rating	"An indication of the difficulty of a golf course for the scratch player under normal course and weather conditions"
Slope Rating	"An indication of the relative difficulty of a golf course for players who are not scratch players compared to players who are scratch players"
Score Differential	"The difference between a player's adjusted gross score and the Course Rating, reflecting the Slope Rating and the playing conditions calculation."

The 113 in the formula is the Slope Rating of a course "of standard playing difficulty", per the Handicap Index definition. In Australia the Course Rating is called the Scratch Rating (more on that below).

Step 2: Adjusted Gross Score (net double bogey)

You don't feed your raw gross score into the formula. You feed in your Adjusted Gross Score. The Rules of Handicapping define it as "A player's gross score, including any penalty strokes, adjusted for when: The player exceeds their maximum hole score, A hole is not played, or A hole is started but the player does not hole out."

For a player with an established Handicap Index, USGA Rule 3.1b caps each hole at net double bogey:

Par of the hole + 2 strokes + Any handicap stroke(s) that the player receives on that hole

USGA also says: "A net double bogey is equal to the lowest score on a hole for which the player would achieve zero Stableford points." And "There is no limit to the number of holes in a round where a net double bogey adjustment may be applied."

Which handicap sets the strokes for this? Rule 3.1b: "The player's full, unrestricted Course Handicap should be used for all applications of net double bogey adjustments." Need yours for the tees? The course handicap calculator does that sum (US-style Course Handicap).

If you enter hole-by-hole scores, the rule says the adjustment happens "Automatically". Otherwise you do it yourself before you submit.

Steps 3 and 4: Apply the formula and round

USGA Rule 5.1a, for an 18-hole score, written in plain text the way the USGA's own FAQ writes it:

Score Differential = (113 / Slope Rating) x (Adjusted Gross Score - Course Rating - PCC adjustment)

Rounding, also Rule 5.1a: "rounded to the nearest tenth, with .5 rounded upwards".

Nine holes has its own version under Rule 5.1b. If you're working one of those, check with your club or association.

Worked example (made-up numbers)

Example only. Made-up golfer, made-up tees. Course Handicap 18 (one stroke on every hole), Course Rating 71.0, Slope Rating 128, PCC 0. Gross score 92, with two big holes:

Hole (example)	Par	Strokes received	Net double bogey cap (par + 2 + strokes)	Actual score	Counts for handicap
6	4	1	7	9	7 (2 strokes off)
14	3	1	6	6	6 (no change)
Other 16 holes				77	77 (all under their caps)
Total				92	90 Adjusted Gross Score

Now the formula:

Step	Working	Result
113 / Slope Rating	113 / 128	0.8828125
Adjusted Gross Score - Course Rating - PCC	90 - 71.0 - 0	19.0
Multiply	0.8828125 x 19.0	16.7734375
Round to nearest tenth		16.8

Same round on a day the PCC came out at +1: 90 - 71.0 - 1 = 18.0. Then 0.8828125 x 18.0 = 15.890625, which rounds to 15.9. Tougher day, better differential.

Want to check your own? Pop it into the score differential calculator.

The PCC adjustment

PCC is the playing conditions calculation. USGA Rule 5.6 says it "determines whether playing conditions on the day differed from normal conditions to the extent that an adjustment is needed to compensate."

What the rule says about it:

It "requires at least eight acceptable scores to determine if an adjustment is required" and "Equals zero if fewer than eight acceptable scores are submitted."
It "Includes only acceptable scores submitted by players with a Handicap Index of 36.0 or below."
It "Can determine an adjustment of -1.0, 0.0, +1.0, +2.0 or +3.0 and is applied in the calculation of Score Differentials for all players."

You don't work the PCC out yourself. It's a daily calc run by the system. You just plug the day's number into the formula.

Step 5: How differentials become a Handicap Index

Once you've got 20 scores, USGA Rule 5.2b says: "Average the lowest 8 of the most recent 20 Score Differentials (which include any adjustments for exceptional scores and/or a Committee review) and round to the nearest tenth."

Then there's a cap check against your Low Handicap Index: "If the difference is greater than 3, the soft cap calculation is applied. If the difference is greater than 5 after application of the soft cap, then the hard cap is applied."

Fewer than 20? Rule 5.2a uses this table:

Number of Score Differentials in scoring record	Score Differential(s) used	Adjustment
3	Lowest 1	-2.0
4	Lowest 1	-1.0
5	Lowest 1	0
6	Average of lowest 2	-1.0
7 or 8	Average of lowest 2	0
9 to 11	Average of lowest 3	0
12 to 14	Average of lowest 4	0
15 or 16	Average of lowest 5	0
17 or 18	Average of lowest 6	0
19	Average of lowest 7	0
20	Average of lowest 8	0

So a bad round only counts toward the average if it lands in your lowest 8. Your Index can still move when an older round drops out of your most recent 20. A good round can bump a higher differential out of the 8 and pull your Index down.

Australia: Gross Differential, Scratch Rating, Daily Handicap

Same World Handicap System, Aussie wording. Golf Australia calls it a "Gross Differential" and says it is "our calculation of the handicap you played to in that round."

The inputs are different. Golf Australia's 18-hole formula (written here in plain text) is:

Gross Differential = ((36 - Stableford Score) + Daily Handicap + Par - (Scratch Rating + PCC)) x (113 / Slope Rating)

That runs off your Stableford score and your Daily Handicap, not an Adjusted Gross Score. And where the US says Course Rating, Golf Australia says Scratch Rating. Golf Australia also notes the PCC "is also referred to on www.golf.com.au and in the GA Official App as 'Daily Difficulty'."

Your GA Handicap is then the "Average of best 8 of the 20 most recent 18-hole 'Gross Differentials'", unless the cap applies.

One more thing for Aussie readers. Your Daily Handicap has its own Golf Australia formula. Don't swap in the US Course Handicap formula. Golf Australia CONNECT "will calculate it all for you", and your club has the look-up chart.

A scramble score isn't a differential

A team scramble or Ambrose score is not a differential for anyone. The team picks the best shot, so nobody played their own ball all the way round. Golf Australia's rule for team events that do count is that each golfer plays their own ball and "It is each golfer's individual score that is used for handicapping." Full rundown: does a scramble count for handicap.

How do you calculate a score differential?

Take your Adjusted Gross Score, subtract the Course Rating and the day's PCC, then multiply by 113 divided by the Slope Rating. Round to the nearest tenth, with .5 rounded up. That's USGA Rule 5.1a. The score differential calculator does it for you.

What is Adjusted Gross Score?

Your gross score, penalty strokes included, adjusted for any hole over your maximum hole score, any hole not played, and any hole you started but didn't hole out. Once you have a Handicap Index, the maximum on each hole is net double bogey: par plus 2 plus any strokes you get on that hole.

How many differentials make a Handicap Index?

With 20 or more scores, the lowest 8 of your most recent 20, averaged and rounded to the nearest tenth (USGA Rule 5.2b). With fewer, Rule 5.2a uses a sliding table that starts at 3 scores.

Is a score differential the same in Australia?

Same idea, same 113 and Slope, same best 8 of 20. But Golf Australia calls it a Gross Differential, works it from your Stableford score and Daily Handicap, and uses the Scratch Rating instead of the Course Rating. Check your Golf Australia record or ask your club rather than running the US formula.

Keep reading

Keep your team days, card your handicap rounds

For a team Ambrose or scramble, Scrambled Eggs keeps the team score, whose shot got used and each player's shot contribution on one phone per group, works out the Team Ambrose handicap, and saves the round to history. For handicap rounds, use your own card.

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