October 2022: Different Day, Different Differential

By Kelly Neely, Sr. Director, Handicapping & Course Rating

In educating golfers about the complexities of World Handicap System, we’re always looking to create ‘light bulb moments’ – flashes of realization and clarity. These can result in blinding floodlights or barely flickering 25-watts; we’ll take whatever we can get and call it enlightenment.

No WHS subject has more light bulb potential than understanding what a Score Differential is. Folks, once you embrace the Score Differential, you just might find yourself – if such a place exists – on the Happy Path to Handicapping. (Warning: Even the Yellow Brick Road had its Flying Monkeys).

But first a definition from the Rules of Handicapping –

A Score Differential is the difference between a player’s adjusted gross score and the Course Rating, reflecting the Slope Rating and the playing conditions calculation. It is the numerical value attributed to a score achieved on a golf course on a specific day that is posted into the player’s scoring record.

After all of that, we’re not sure it helps or hinders to expose the formula, but what the heck. We’re so fond of mathing here at the OGA that yes, we’ve turned it into a verb.

Score Differential = (113 / Slope Rating) X (Adjusted Gross Score – Course Rating – PCC adjustment). This value is rounded to the nearest tenth, with .5 rounded upwards.

Where can this magical value be found? Check out your scoring record (under Stats) and stare at it for a few seconds like you’re at the Optometrist’s office trying to focus on an eye chart. Look for the Differential. It will be a number taken to one decimal place, such as 18.1. Note that this number looks nothing like your scores.

In fact, it’s far more important.

What exactly does this value mean and why is it significant? Simply put, a score of 85 on a difficult course may actually be more impressive than a score of 80 on an easier one. The Score Differential is what allows this to be captured.

Now don’t you feel better about your 85?

A Score Differential is where all the nerdy numerical components blend together into a delightful mashup like a morning smoothie of indeterminate hue. You know, the kind that tastes funky but is good for you.

Here’s more to add wattage to your light bulb:

  • Golf is thoroughly unique because each field of play is different. We are not playing on a football field or a basketball court or a baseball diamond. Each golf course is one-of-a-kind. Luckily, we have the ingenious Course Rating System that allows us to evaluate the playing difficulty of all courses in a standardized way, but each winds up with their own specific set of numbers. Such is the yin and yang of golf: it’s the coolest sport ever, but also complex.
  • When a golfer has a full scoring record of at least 20 rounds, eight of the lowest Score Differentials will be chosen to calculate their Handicap Index. Note that we didn’t say the “lowest scores” will be chosen! Getting up close and personal with Score Differentials will tell you why a Handicap Index is calculated the way it is (take your starred differentials, add together, and average them. That’s your Index).
  • See the very interesting number 113 in the formula above? In geek terms, it’s called a mathematical constant because it is as ever-present as finding trouble on Hole No. 4 at the OGA Golf Course. Back in the early eighties When Slope and MTV Were Born, a national slope standard of 113 was established based on 1.13, which research at the time showed was the average stroke increase from one handicap to the next. That value held – unlike Glam Metal – and was brought into the WHS.
  • Note that par does not make an appearance in the formula of a Score Differential. Thankfully it doesn’t need to. Don’t worry, it rears its sometimes-problematic head once you have your Handicap Index in hand and you’re ready to play.
  • A golfer who plays a variety of courses will see more volatility in their Score Differentials. It stands to reason that if you’re lucky enough to play a diverse slate of courses you’ll more often see a rise and fall in your Differential column than your friend steady-Eddie, whose Differentials remain relatively constant because he plays the same course all the time. But watch how Eddie’s scoring record is impacted when he’s feeling brash and moves back to play the tips. He’ll likely score higher due to the longer tee, but his Differential will be lower because of the higher Course / Slope Rating. A puffed-out chest might ensue.

Kids, let’s do some mathing! Here’s a good example of a player on two different courses, but with the same score:



And here’s an example of two players with two different Handicap Indexes, on two different courses:


If your eyes haven’t rolled completely out of the back of your head yet, here’s a question we recently received that illustrates the impact of a single Score Differential to a Handicap Index –

Q: After my most recent round which was a better score than most, I was expecting a handicap drop, instead I got an increase. Why? Was this correct?

A: We know how disappointing it can be (for some of us) to expect a drop in your Index and not get it. The reason your Handicap Index went up was because you added a 73 with a Differential of 14.7, but that score replaced a 70 with a 13.2 Differential. That 70 was your 20th score, now out of contention and sadly, a fading memory. When you post a score, good or bad – yes, even ugly – you always must consider the round that cycled out. Was it one of the scores chosen to calculate your Index? Was it lower than all the scores before it? Was it higher? Your score that dropped off had the lowest differential of your full scoring record, so we’re sorry to say that your Handicap Index has gone from 16.8 to 17.9 – up by 1.1.

And now because we know you’re exhausted (possibly napping) from all this engagement with your light bulb, we’ll end with this:

Scores are how you think you’ve played. Score Differentials are how you’ve actually played.