To get an understanding of what Rating and Slope mean to you, we must first get an understanding of what these two numbers represent. As well, we need to have an understanding of what a handicap represents.
The rating of a course is meant to show what a scratch golfer (0 handicap) should average on a particular course from a particular set of tees. The Slope, intern, is how much more difficult the course is for a bogey golfer (18 handicap) versus a scratch golfer.
A the slope for what is considered an average course is 113. Why this is the number specifically is relatively arbitrary. But, this number is derived by taking a courses bogey rating minus the courses scratch rating and multiplying that number by 5.381. Whether you know or not, every course is also given a bogey rating as well as the standard scratch rating that is shown on the scorecard. So, looking at this, you can derive that the average course in America has a rating of 72.0 for scratch golfers and a rating of 93.0 for bogey golfers. (93-72) x 5.381 = 113.
The obvious question to ask here, is why would 93 (+21) be the average score for a bogey golfer. Wouldn’t you think that someone with an 18 handicap would average 18 over on an average course? Well, the answer to that is that is not how a handicap works. Handicaps only represent the average of the top 10 scores out of your last 20. So, theoretically, you should only be shooting your handicap or better in the top 25% of your rounds. Furthermore, because of the nature of golf and the way bad rounds spin out of control, your worst rounds are usually way further away from your median score than your good rounds are. With that understood, we understand that the average score for an 18 handicap on an average course is 21 over.
Many aspects of a golf course can punish a bogey golfer much more disproportionately that they do a scratch golfer. A bogey golfer isn’t as long, so distance has a more negative effect on a bogey golfer. Bogey golfers have a much more difficult time making good shots out of sand and other hazards, so hitting those areas is disproportionately punishing on bogey golfers. And finally, a scratch golfer is more accurate and manages the course better, so a bogey golfer is much more likely to find water hazards, unplayable lies, and OB, which is accompanied by penalty strokes. So, to say that a bogey golfer should be 21 strokes worse than a scratch golfer no matter the course would not be accurate, and this is where slope would come in. On a course like The Classic at Maddens, which has a slope of 148, a bogey golfer would be expected to shoot 28 strokes higher on average than a scratch golfer. The higher the slope, the larger the gap between a scratch golfer and a bogey golfer.
The more you know…