Understanding Strokes Gained Statistics

During a PGA TOUR broadcast, you have likely seen something like this:

It’s a relatively straight forward graphic.  In a nutshell, Rory hit the ball way better than anyone, while also putting fairly well, and thus creating a 4.1 advantage in strokes against the rest of the field.

That’s all well and good.  But if you’re like me, you also want to know what that exactly means and how those numbers are created.

Allow me to provide a crash course in what is actually a fascinating and very useful set of metrics—check out this Golf Digest piece if you want to read how strokes gained was actually developed.

First, how the number is calculated.

Basically, there have been benchmark standards developed based on the tracking of millions of shots taken by PGA professionals during tournaments.  These benchmark measurements are in “strokes to hole” increments, meaning based on the current lie of the golf ball and distance from the hole, it takes, on average, “X” number of strokes to get the ball in the hole.  These benchmarks have been developed for every possible position and lie on a golf course—thank you big data!

Let’s use an example, a 430-yard hole has a stroke to hole value of 4.05.  This is based on lie (tee) and distance to the hole (430 yards).  After a 290 yard drive into the fairway, the lie is now “fairway” and distance is 140 yards.  The stroke to hole value for that lie and distance is 2.91.

We already know a 290-yard drive down the middle of the fairway is good.  But we can put an actual value to the drive by doing some simple math.

4.05 (position and lie #1) – 2.91 (position and lie #2) – 1 = +0.14

+0.14 is the strokes gained with that first shot!  Nice!

Let’s do it again for the next shot.

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We already know our first number based on lie (fairway) and distance (140 yards) is 2.91.  Now let’s say we push our second shot to the right into a green side bunker—let the expletives fly and take a moment to regroup.

Now our lie is 15 yards from the hole and in the sand, which is a stroke to hole score of 2.48.  We know that was a bad shot, but how bad compared to what typically happens?  Let’s do the math!

2.91 (position and lie #2) – 2.48 (our sand bunker lie) – 1 = -0.57

Ouch.  There goes our +0.14 strokes gained off the tee.  Now we’re suddenly at -0.43 strokes gained against the benchmark.  That shot was pretty costly.

Now imagine doing this for every shot.  It will start to put together some very thorough and telling stats.  This is the value of strokes gained.

Again, typically a broadcast will give the very generic “tee to green” strokes gained.  This is obviously built using every shot taken by a player that is not a putt.  Which is fine, but also kind of lazy.  There are more telling numbers behind that simple statistic.  If they really wanted to tell the story of how the leader built his lead against the field, they could break down his strokes gained from multiple lies and distances.

Next up, using the strokes gained calculator and metrics ourselves to understand our own games!

Cover Photo via Flickr