One of the most important components in the calculation of your handicap is the rating and slope
of the course that you play. The slope and rating numbers are used to measure a course's difficulty. The rating
represents the average score a scratch golfer (handicap of 0) would shoot on the course, and the slope represents
the increased level of difficulty a bogey golfer (handicap of 18) would face as compared to a scratch golfer.
For more information about the basics of the rating and slope please see the
Rating and Slope article
in this section.
So how does a course end up with a rating of 72.1 and slope of 134 versus a rating of 68 and slope of 115?
Actually, the calculation is not at all what you would expect, and in the article below we shed light on the
Most golfers picture the course rating as being calculated by a group of scratch golfers who play the course,
and turn in their scorecards to an official who takes the average. It may surprise you, but no actual playing is involved
in the calculation of the course rating. The rating is solely a yardage formula with some slight adjustment for
This is because yardage should have the greatest effect on the game of a scratch golfer. Woods on
the right or water in front of the tee do not bother a scratch golfer very much. But, the difference in trying to make a birdie
from 120 yards versus 160 yards can be quite significant. For their calculations, the USGA
employs an imaginary ideal
scratch golfer who drives the ball 250 yards (225 of carry, 25 of roll), can hit
his/her second shot 220 yards (200 and 20), tends to draw the ball and is strong at all phases of the game.
The Scratch Yardage Rating
is the simple calculation, as it is essentially the course yardage divided by 220
plus 40.9. This rating may be adjusted for several factors, including whether a ball will roll longer or shorter
than 25 yards, the number of elevated or dogleg holes, prevailing wind and altitude, etc. In essence, any factor that
will alter the scratch golfer profile (to hit farther or shorter than 250 yards) will affect the Scratch Yardage
The Scratch Obstacle Rating
is considerably more complex to calculate. Each rater receives a form with 11 boxes
for each hole (that's 198 boxes in total). Into each box is entered a number representing an obstacle value.The standard is 4.
A lower value means the difficulty posed by, say, trees, is less than standard. A 10 means the hole is etched into a
jungle. The obstacles for each hole considered include: topography, fairway, recoverability & rough, out of bounds,
water hazards, trees, bunkers, the green target, green surface, and a psychological factor. Each of these is weighted
and the 18-hole sum of weighted values is multiplied by 0.11. Raters then subtract 4.9 to determine the Scratch
The sum of the Scratch Yardage Rating
and Scratch Obstacle Rating
becomes the Course Rating.
Let's take a simplified example of a 6000 yard course (with no adjustments) that has average-type obstacles on every
hole. The Scratch Yardage Rating
would be 6000/220 + 40.9 = 68.2. The calculation of the Scratch Obstacle
is complex, but in this case would emerge around 3.0. Thus, the Course Rating would be calculated
Yardage versus Obstacle Ratings
While over 95% of the rating comes from the yardage, the swing in course rating
often comes from the obstacles. For example, if the course suddenly became 400 yards longer, the Scratch Yardage
Rating would incrase from 68.2 to 70.0, or 2.6%. In contrast, if our average course obstacles (rated 4) became
much more difficult (rated 8) our Scratch Obstacle Rating would increase from 3.0 to 10.9, or over 250%.
So, for the slope, do we at least send bogey golfers out to play and compare their scores to the course rating?
No. The USGA has created a model bogey golfer as well. The USGA's bogey golfer is meant to represent a golfer
with a Handicap Index of 17.5 to 22.4. They can hit tee shots an average of 200 yards and can reach a 370 yard
hole in two shots.
Similar to the course rating, the slope is made up of a Bogey Yardage Rating
and a Bogey Obstacle Rating.
The Bogey Yardage Rating
is once again based on yardage, but uses a different formula. This time,
it is equal to the course yardage divided by 160, plus 50.7. The Bogey Obstacle Rating
is based on the
same 11 factors, only they are weighted differently for each hole. The sum of the factors for all 18 holes is then multiplied
by 0.26 and then 11.5 is subtracted. Note that obstacles are now much more significant because the 0.26 used
is two and a half times as much as the 0.11 factor used for the Scratch Obstacle Rating
Once again the Bogey Yardage Rating
and Bogey Obstacle Rating
are added together to create
the Bogey Rating. But there is still one more calculation to go. The difference between the Bogey Rating
and the Course Rating is multiplied by 5.381, and the result is the slope (i.e. [BR-CR]*5.381=slope)
Why 5.381? Using this number as a multiplying factor will produce Slope Ratings of 113 when the differential
between the Bogey Rating and Course Rating is 21.0 (The expected difference in score on an average course
between our model scratch golfer and bogey golfer with handicap between 17.5 and 22).
A Slope of 113 (actually 1.13) also is the empirically derived regression value of scores played
on standard American golf courses. So it all ties together.
Let's revisit our 6000 yard course, this time with our bogey golfer in mind. The Bogey Yardage Rating
is 6000/160+ 50.7, or 88.2. The same average obstacles now become a Bogey Obstacle Rating
of 7.2. Together,
the Bogey Rating is 95.4, 24.2 points higher than our Course Rating of 71.2. 24.2 Multiplied by 5.381,
our slope is calculated as 130.
A lot of number crunching to be sure, but still this process is not an exact science.
What it does do, though, is bring the handicap system to a new level of accuracy across handicaps.