Score Differential & Course Handicap Calculator
Work out a round's score differential and your course handicap using the World Handicap System formulas.
Score differential (one round)
Course handicap (from your index)
How it works
The World Handicap System turns a raw score into two different numbers, and it's easy to mix them up. A score differential measures how you played one specific round, adjusted for how hard that course was. A course handicap tells you how many strokes to take on a specific course, given your existing handicap index. This tool computes both.
Score differential is (score minus course rating) times 113, divided by slope rating. Slope 113 is the baseline difficulty, so a course rated exactly at its slope contributes nothing extra to the formula beyond the raw score-to-rating gap. Worked example: shoot a 90 on a course rated 72 with a slope of 130. That's (90 − 72) × 113 / 130, which comes out to 15.6. A tougher-than-average course (slope over 130) will produce a lower differential than an easier one for the exact same score, because it's accounting for the extra difficulty.
Course handicap is your index times slope divided by 113, plus the difference between course rating and par. Take a 15.6 index to a course rated 72 with a slope of 130 and par 72: that's 15.6 × 130 / 113, plus zero since rating equals par, which rounds to 18. That's the number of strokes you'd actually take off your gross score on that course that day.
One important distinction: your official handicap index isn't just your last round. It's calculated from roughly the average of your best 8 differentials out of your last 20 posted rounds, and it comes from your club or association's official posting system, not from a single differential. This tool computes the building-block math (one round's differential, or a course handicap from a known index); it's a way to understand and sanity-check the numbers, not a substitute for posting scores properly.
FAQ
What counts as an "adjusted gross score"?
It's your actual score with a cap applied per hole (net double bogey, under the current WHS rules) so a single blow-up hole doesn't wreck your whole differential. For casual use, most beginners just enter their actual score, but know that official posting applies that per-hole cap first.
Why does slope matter so much?
Slope rating measures how much harder a course plays for a bogey golfer relative to a scratch golfer, on a scale roughly from 55 to 155, with 113 as the average. A high-slope course punishes higher handicappers more, so the same gross score there should convert to a better (lower) differential than on an easy, low-slope course.
Is my course handicap the same everywhere I play?
No. Your handicap index stays constant until your next posted round updates it, but your course handicap changes at every course, and even at every set of tees, because rating and slope differ. Always recalculate for the specific tees you're playing.
Can I use this to get an official handicap index?
Not directly. An official index requires posting scores through your golf association or club system, which tracks your last 20 rounds and applies the full WHS calculation automatically. This tool is for understanding the math behind a single round or a single course handicap conversion.
For more on scoring and course strategy, see how to keep score in golf and what a handicap is, par, birdies, and bogeys explained, and course management for beginners.