Handicap
Golf Score Differential Calculator
How good that round was, as a score differential.
Unofficial estimate. Not affiliated with or endorsed by the USGA, The R&A, or GHIN.
The short answer
A 90 on a course rated 71.2, slope 128, is a score differential of 16.6. Against an index of 14.2 that is 2.4 higher.
How it’s calculated
18-hole differential = (113 ÷ slope) × (adjusted gross score − course rating − PCC)
Worked example: (113 ÷ 128) × (90 − 71.2 − 0) = 16.597, which rounds to 16.6. With 20 scores in the record, if this replaced a differential that sat on a 14.2 index, the index would move by about 0.3. That sketch is not a new official index.
Nine-hole scores add an expected differential for the other nine. The only USGA example published in plain numbers is an index of 14.0, a nine-hole differential of 7.2, and an 18-hole result of 15.7, so the expected half is 8.5. This page uses (index + 3) ÷ 2, which hits that example, and says when it may not match official software.
Net double bogey is par + 2 + the strokes your course handicap gives you on that hole. Hole-by-hole entry applies that cap before the differential is calculated.
Rules this page does not fully apply
- Playing Conditions Calculation is not worked out here. It stays at 0 unless you type the −1 to +3 number your golf association published for that day.
- Handicap Committee adjustments are not applied.
- The official expected-score table for nine-hole rounds is not published. This tool adds (Handicap Index + 3) ÷ 2, which matches the USGA’s published example: an index of 14.0 has an expected nine-hole differential of 8.5, and 7.2 + 8.5 = 15.7. Other indexes can differ from official software.
- Rounds of 10 to 17 holes are not calculated. Official software fills the holes you did not play with an expected score.
- Soft and hard caps are applied to the final figure only, and only if you enter a Low Handicap Index and the list has 20 differentials. This page does not store a 365-day history.
- Exceptional score reduction replays the rounds on this page, oldest first. It cannot see an index from scores you left off, unless you enter a starting index. The check uses the running index before caps.
- The pre-2020 USGA formula multiplied the average by 0.96. The World Handicap System does not. This tool does not use 0.96.
Questions golfers ask
What is a score differential?
It is the portable value of one round. A 16.6 differential is not a score of 16.6. It is how far that adjusted score sat above the course rating, scaled so a slope of 113 stays as-is and a harder slope shrinks the gap. Handicap indexes are built from differentials, not from raw scores.
Do I enter my gross score or an adjusted score?
Enter the adjusted gross score: your gross score after any hole above net double bogey has been cut back. If you type hole-by-hole scores, this page applies that cap from your course handicap and uses the adjusted total. A score you already adjusted on the card can go straight into the score box.
What is the playing conditions calculation?
On a day when scores across the course are unusually high or low, the association can add a PCC from −1 to +3. This tool does not calculate it. Leave PCC at 0 unless you know the number published for that day. A +1 makes the differential lower, because the day played harder.
Can a differential be negative?
Yes. If your adjusted score beats the course rating, the differential is negative. That is a better-than-scratch round on a standard-difficulty course. Negative halves round toward zero, so −1.55 becomes −1.5.
How much can one round move my index?
With 20 scores, the index is the average of the best 8 differentials. One new differential changes that average only if it lands in the best 8. A rough size of the move, if it replaced a differential sitting on your index, is the gap divided by 8. The index calculator is the place to run your real list.
How do 9-hole rounds work?
The nine holes you played produce their own differential. An expected differential for the other nine, based on your index, is added, and the sum is an 18-hole differential. The official expected-score table is not published. This page uses (index + 3) ÷ 2, which matches the USGA’s example of an index of 14.0.
Is this the number I post?
No. You post a score to the association that runs your index. They calculate the differential, including the day’s playing conditions. This page is an estimate you can check before or after that. It is not a GHIN posting screen, and it is not issued by the USGA or The R&A.