US Handicaps - How to Calculate

First of all, I’ve been a bit busy with work over the past few weeks, hence the delay in getting this post up. Normal service should now be resumed.

I have created this separate post just to detail how to calculate a US handicap, as combining it with my view on US Handicaps would have resulted in a lengthier version of War and Peace. Believe it or not, this post is an abridged version, I only cover off the basics in this post.

To get a current US handicap, you need to find the “Handicap Differentials” of the last 20 rounds. Take the best 10 of these 20 Handicap Differentials (the 10 lowest numbers), and average them. Then multiply this figure by 0.96, round up to the nearest 0.1, and you have a handicap. That is the easy part. Figuring out the handicap differential for each round is a bit more tricky, although most courses have charts that can be referenced against.

First of all, you need to figure out the Adjusted Gross score of a round. This is similar to the Stableford Par Adjustment system in the UK, where scores worse than net double bogey are reduced to net double bogey, in line with the strokes received in accordance with the stroke index of the course. However, in the US, for single figure players each score is reduced to double bogey, rather than net double bogey. Bizarrely, for 10-19 handicappers, scores worse than 7 are rounded down to a 7, 20-29 handicappers, scores worse than 8 are rounded down to 8, and so on. This gives no allowance for whether the score occurs on an easy par 3 with no hazards, or a tough-as-nails par 5 with water snaking the hole, bunkers all around the green, and alligators popping up at random intervals. However, I hope never to be in any of these handicap categories so it’s not my concern.

Once you have an Adjusted Gross score, you need to know the Course Rating and the Slope Rating. I’ll deal with each of these individually.

The Course Rating is meant to be the score a scratch golfer would be expected to go around the course in, in the average of the best half of their last 20 rounds. It is calculated by looking at the yardage of the course, then adding yards based on difficult aspects (hazards, uphill shots, into the prevailing wind, and so on), or subtracting yards based on benefits (lack of hazards, downhill, downwind, and so on). At the end of all of this, the course will have an “Effective Length”. This figure is then divided by 220, and then 40.9 is added to it, and this value (once rounded to the nearest 0.1) is the Course Rating. It is a lot more scientific than I have just detailed, however I fail to believe that every course has a completely accurate Effective Length, as even a difference of 22 yards in the Effective Length can add 0.1 to the course rating.

The Slope Rating indicates the degree of how much more difficult the course gets for non-scratch golfers. Generally, on difficult courses a 21 handicapper will take greater than 21 more shots than a scratch player, whilst on an easy course a 21 handicapper may be expected to go round in less than 21 more shots than a scratch player.

The same principle of finding the Effective Length of the course is applied for a Bogey Golfer (generally a player with a handicap of around 20). This Effective Length is then divided by 160, and then 50.7 is added to it, the value once rounded to the nearest 0.1 is the Bogey Rating.

We’re getting there, just a little bit more to go. Take the difference between the Course Rating and the Bogey Rating, multiply it by 5.381, round it to the nearest 0.1, and this result is the Slope Rating.

A course of average difficulty has a Slope Rating of 113, which indicates that a Bogey Golfer is expected to take 21 more shots than a scratch golfer. Slope Ratings can range between 55 and 155 (Carnoustie Championship is 145).

Finally, we have what we need to calculate the Handicap Differential. Take the Adjusted Gross, subtract the Course Rating, multiply it by 113, then divide by the Slope Rating.

So in short; Handicap Differential X = ROUND(AG – ((SEL / 220) + 40.9) * 113 / ((((BEL / 160) + 50.7) - ((SEL / 220) + 40.9)) * 5.381),1), where AG is the Adjusted Gross, SEL is the Scratch Effective Length, and BEL is the Bogey Effective Length.

Following on, Handicap = ROUNDUP((X(1) + X(2) + X(3) + X(4) + X(5) + X(6) + X(7) + X(8) + X(9) + X(10)) / 10 * 0.96,1), where X(N) are the 1^st to 10^th lowest handicap differentials from the last 20 rounds of golf.

Easy, isn’t it?