Slope and Rating: What do all of these numbers mean?
By Bryan K on 12/20/12
Slope and rating are both relevant numbers when deciding how difficult a course is. Knowing what these numbers mean can turn them into effective tools. Not knowing what they mean can turn them into serious obstacles.
Let's start with the basics.
Scratch players have it easy here because they can refer to one simple number to determine how difficult a course is. The course rating was developed exclusively for those scratch players, but there is one slight problem — the course rating was developed with no other intent than to rate the length of a course. Apparently the golf gods over at the USGA have all determined that in order to be a scratch golfer, you have to be very accurate with all of your clubs. Therefore, silly little obstacles like greens tucked behind bunkers with a giant lake behind are irrelevant to the scratch golfer. I guess the USGA feels that scratch golfers never hit into such obstacles. They always hit the green when they are in range, and they always two-putt. And if they hit the green before they are in range or if they ever one-putt, that means that they are better than scratch.
Now it gets tricky when we start talking about slope. The slope is essentially a measurement of all of the things besides distance that make a course challenging. This can include water hazards, bunkers, the curvature of the greens, even the prevailing weather conditions. The slope essentially tells us how many strokes over the course rating a bogey golfer should play. But they couldn't just give us a straight number to accomplish that extremely difficult feat. No, they had to make it a number that you had to divide by some random number picked out of the clouds, say 5.38, to come up with the number of strokes that a bogey golfer should shoot over the course rating.
But wait, it gets even better. This number that the bogey golfer should shoot over the course rating doesn't actually have a name. It is simply the number that you have to add to the course rating in order to arrive at a course's bogey rating. So, since it doesn't have a name, we'll assign it an acronym. Henceforth, it will be referred to as NTYHTATTCRIOTAAACBR.
The bogey rating is the important number. And it better be important if I have to go through all of that work to get it. It tells us essentially what an 18 handicap should shoot on any given course. And those of us who are not 18 handicaps can adjust that number based on how far over or under 18 we are. In fact, we can use the algebraic law of proportions in order to come up with that number.
What? Algebra? Nobody told me I would need to use algebra to play this game.
But wait, it gets even better (again). The golf gods over at the USGA decided that making the process this complex wasn't enough. They had to assign a different random number for women to divide by in order to come up with a specific course's NTYHTATTCRIOTAAACBR. For women, that number is 4.24.
Sheesh. Can we stop now?
Now that we got all of that mumbo jumbo out of the way, the question that needs to be asked is ... how do we use all of this information?
Contrary to popular belief, I do not believe that a course's slope should have any relevance whatsoever as to what tees a player should play. That should be determined by distance alone. If you can hit the ball 125 yards, then the entire challenge involved in the game of golf resides in how far out you can make those tricky shots (that and putting). So even if a course has tiny island greens on all 18 holes that give it a slope of 150, a player should still determine what tees to play based on how many shots it will typically take him to get within range of those itty bitty greens.
However, a course's slope does have a use. And at least for a bogey handicapper like me it's pretty simple. If I want to get a glimpse of how difficult a course is, I simply use the formulas above to find the bogey rating (course rating plus NTYHTATTCRIOTAAACBR). And then I try to beat that score. So If I got to a course that has a rating/slope of 71.1/120, I will divide 120 by 5.381. That gives me 22.3. If I add that 22.3 to the course rating (71.1), I get a bogey rating of 93.4. That's the score I need to beat in order to beat my handicap. And if you think about how handicap is calculated, a golfer will only beat his handicap an average of five out of ever 20 rounds. So that is a very realistic goal that every golfer can set for each and every round.
But what if you're not a bogey golfer? Well, then you will need to either use the law of proportions which I described above, or you will need to use the course handicap calculator at usga.org to find out what you need to shoot to beat your handicap.
Wait. And what's this stuff about a course handicap?
This was written by Bryan Kautzman, a reader/follower/fellow oober and the opinions are 100% his and do not reflect those of oobgolf in anyway. Enjoy! I'm sure he's ready for your feedback.
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[ comments ]
joe jones says:
Wow. Where did all this come from? I have played with Bryan and he never once mentioned all of this to me. Perhaps he recognized that I already had altogether too many pithy little things rambling around in my senior brain to absorb that much data.All I ever do is enter my score on Oob and let that handicap system do it,s job Seriously Bryan. Great article
I think I understood everything up to the point where you said "relevant numbers" ;)
Nice job, Bryan K.
Great article Bryan, but can i ask where you read that the course rating only takes length into account? Everything i've read (becasue i haev wondered where these numbers came from) states that the rating also accounts for all aspects of a course that impact difficulty. The best explanation i've seen is on the USGA website.
Matt McGee says:
Great article. I wasn't aware of the formula for the slope. Thanks, Bryan.
I once found this site ( www.popeofslope.com/courserating/system.html) which has plenty of info on slope rating. It can get pretty detailed and technical, but if you're on the nerdy side of golf, it's good stuff. :)
As far as wanting a score to improve my handicap, it all comes back to finding a differential that is somewhat lower than your highest differential that counts in your 20 scores. Also, shooting good rounds on tough courses generally makes a difference!
You gotta love the USGA!
Good article, but you make it more complicated than it really is, with that 5.381 number.
The slope is called that way because is the linear coefficient in the straight line (y = ax + b, where a is the slope and b is the rating, or law of proportion as you call it) between what the score of a scratch golfer and any golfer (including the bogey golfer) should ideally be on a course of a certain difficulty. The higher the difficulty, the steeper that line is on a graph, and the greater the slope. The closer one is to a scratch golfer, the more important the rating is, and the higher the handicap, the more important the slope is. The standard slope (that is the difficulty of a standard course, not easy, not hard) is 113 so anything higher than 113 is hard(er) and anything below 113 is easy(er).
As for any golfer course handicap, it's simply: index * slope / 113 and the number than gets entered in the golfer's handicap calculation, the differential is (ESC score - rating) * 113/slope, so one gets a lower differential, resulting in a lower handicap index, when playing more difficult courses, with the same score. But, one point of rating is more significant than even 5 points in slope depending on one's index, as you can see with the algebra. Yes, there is algebra (or tables at the golf course or online) involved! :)
By the way, you often see rating such as 68.9, 69.2, etc... for courses where the par is 72, for some forward tees. This means that a scratch golfer is really expected to shoot 3.1 or 2.8 under par (on average) from those tees, because he can cut a dog leg, there is a short par 5 (i.e. around 500 yds, not 600yds), a short par 4 that may be driveable for the scratch player (eg 285yds)...
But those 2 or 3 points of rating difference from 72 also mean that the bogey golfer does not get as much credit (in the differential calculation) if he scores well, for example with an 88 on the par 72 from that same tee. It would take a slope of 131 to make up the 3 points of differential, compared to that rating of 69. In other words compare the same score of 88, on a course with a slope of 113 (standard difficulty) and a rating of 72.0 (long), with a course with a slope of 131 and a rating of 69.0 (shorter yardage). They produce the same differential, and therefore contribute the same way to the golfer handicap index.
Enjoyed the article and the humor, Bryan. and also between it and sjduffers comment above I have learned something. I knew the slope re: 113 means the difficulty and affects your course handicap and the score differential -- but I didn't know that the course rating was based on the length of the course only. Interesting.
zeroSPace - thanks for the link
And I got into golf thinking it was a relaxing game! now I have to do math again?
what? handicap index, course handicap? slope and rating? lateral hazards and front hazards? avoid the what? JUST HIT THE DARN BALL!! LOL
Merry Christmas everyone, enjoy some peace of hart and mind.
joe jones says:
On second thought, I wouldn't be able to do the math anyway. I always thought a polygon was a dead parrot.
Bryan K says:
Mustache Ride: Thanks for the link. You are correct in that rating does take into determination more factors than simply distance, and your linke shows that. Thanks for the correction.
sjduffers: Thanks for the explanation of slope. I knew that algebra cme into play more significantly, but most people just don't get algebra.
I just take the easy way out and add my handicap to the course par rating and use that as my to beat score. If the slope is extremely low, I expect to break my handicap but you know how that goes.........
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