Golf Handicap Calculator
Single round handicap differential from score, rating, and slope.
What it does
A handicap differential rates one round against the course itself. It subtracts the course rating from the adjusted score, then scales by slope so the same play on an easy and a brutal layout yields comparable numbers.
The tool above takes adjusted gross score, course rating, and slope. It returns the differential to one decimal, strokes against rating, and a plain band name for context.
The default of 90 on a 71.2 rating with 128 slope gives (90 - 71.2) x 113 / 128 = 16.6, sitting +18.8 against rating in the average club band. A 113 slope would have read 18.8, showing how tougher slopes cushion road scores.
The formulas follow the World Handicap System maintained by the USGA and The R&A, where 113 is the standard slope and net double bogey caps counting scores. A real index averages the best eight of the last twenty differentials.
How to use
- Enter the adjusted gross score with net double bogey caps applied.
- Enter the course rating for your tees from the card.
- Enter the slope rating for those tees.
- Read the differential first for the portable number.
- Log it with nineteen more rounds; the best eight set the index.
Formula
- score
- Adjusted gross with per hole caps applied.
- rating
- Expected scratch score for those tees.
- slope
- Relative difficulty for bogey golfers; 113 is standard.
Scores outside 50 to 150 and slopes outside 55 to 155 are rejected as entry errors. Unrated rounds and match play concessions need committee guidance before posting.
Worked example
Example: 90 on rating 71.2, slope 128
Adjusted 90, rating 71.2, slope 128.
- Gap: 90 - 71.2 = 18.8 strokes over rating.
- Standard factor: 113 / 128 = 0.8828125.
- Differential: 18.8 x 0.8828125 = 16.596875.
- Round to one place: 16.6. Band: average club range.
- Tool shows 16.6, +18.8, Average club range.
Reference table
| Slope | Differential | Reads as |
|---|---|---|
| 113 (standard) | 18.8 | Higher than at 128 |
| 128 | 16.6 | Example here |
| 140 | 15.2 | Tough course cushions more |
Limits
- One round only. Index math needs eight of twenty.
- Adjusted scores required; raw blowups overstate.
- Nine hole rounds combine in pairs before posting.
- Tee and gender ratings differ; use your own line.
Common mistakes
- Posting raw scores past net double bogey caps.
- Using the wrong tee rating and slope.
- Forgetting slope and comparing raw scores across courses.
- Averaging all rounds instead of the best eight.
- Reading one hot round as the new index.
Try it yourself
Quick checks. Answers sit tucked under each question.
85 on 70.0/113?
(85 - 70) x 113 / 113 = 15.0.
95 on 72.0/130?
(95 - 72) x 113 / 130 = 20.0.
Slope effect: same 90 on 71.2 at 140?
18.8 x 113 / 140 = 15.2.
Questions
What is a differential?
One round rated for course difficulty: (score - rating) x 113 / slope.
What is 113?
The standard slope. Courses above it play tougher for bogey golfers than scratch.
What score caps apply?
Net double bogey: double bogey plus handicap strokes per hole, which bounds blowups.
How is the index set?
Average the best 8 of the last 20 differentials, with adjustments for frequency and conditions.
Can one round set my handicap?
No. It sketches one data point; twenty rounds with eight counting set a real index.
Why did slope 128 lower my 90?
Tougher slopes expect higher scores, so the same 90 converts to 16.6 instead of 18.8 at standard.