The yardage book is the bible for both caddie and player at The Open. The moment the duo reach their ball, out come the yardage books. As a former caddie at Royal County Down and having looped in R&A events, I too know the importance of this little book. However, the book used by the players this week may prove substantially different to the one you've seen or used before.
The yardage book for Royal Portush and the 153rd Open Championship is one with a level of detail I've never seen before - but what makes it so different from the ones us mere mortals can buy in a regular pro shop?
Yardages on sprinklers
There are so many different yardages on each hole, particularly on the Par 4s and 5s, all of which seem very random. This is because they are based off the sprinklers that snake up each fairway, each of which has a number in yards to the front of the green for everyday play that remain year round.
Each fairway yardage is therefore based off the positioning of each sprinkler, leading to small circles with numbers on them dotted along each fairway, making the longer holes look extremely info-heavy - there are 25 of these yardages on the 500 yard Par 4 4th hole and a whopping 45 individual sprinkler yardages on the Par 5 7th. Other yardages are based off notable hole features like the front of bunkers, ridges and mounds.
Seven different versions
You thought there's only one version of The Open Championship yardage book? Think again.
SEVEN versions of the yardage book are available. Each hole has imagery at the bottom of the page of what the players will visually face off the tee but there is a different version for players who came to practice early and those who arrived at the time of the tournament.
Some players will have come to scout out Royal Portrush months in advance before the infrastructure of the stands, cranes and scoreboards were erected. Those who came before this construction will have imagery of the course as they saw it then - without nearly as much infrastructure. Two versions of this book are available, one in yards and one in meters.
Then, come tournament time, new imagery that features all the infrastructure replaces the old imagery which gives the players more aiming points from the tee boxes - two versions of this book are available in yards and meters.
Imagery showing what the players face from the 18th tee box
The remaining three are more simple - two 'all weather' books are available in yards and meters as well as an A4 size yardage books, largely used by broadcasters documenting the action.
Matsuyama and his caddie battle the elements whilst checking their numbers
More detail than the average yardage book
Vistors to Royal Portrush can purchase a course yardage book from the Pro Shop when they come to play. As you can see from the imagery, there is far far more detail included in the players yardage book than the typical pro shop version - for the golfing nerds like myself out there, you can get your hands on a players version of the book from the merchandise tent on site this week.
Having caddied myself in R&A events at Royal County Down, I have seen the difference in detail between the regular RCD strokesaver and the tournament version, but the 2025 Open yardage book is by far the most detailed I've ever seen.
The souvenir version will feature vivid green colors for the fairways and greens as well as a pretty photographed image of the hole above. The professional version has little to no color, with the white background on both the fairway and the green complex allowing for players and caddies to jot down notes throughout the week as they put together their plan of action.
The souvenir yardage book at Royal Troon showing the 2nd hole.
The detail around the green complexes is incredible. Arrows showing the ridges on the green are the norm, but the level of detail in terms of the many humps, hollows and run off areas around the greens is something I've never seen in a yardage book and something you'll certainly never see in a souvenir copy. There isn't a green-side undulation unaccounted for in this book.
The green complex on Calamity Corner, the 16th hole. Notice the lines that are closer together, particularly front right - the closer the lines, the more severe the slope.
Attack angles, runs out and carry numbers
Another thing I've never seen in a yardage book are the measurements relating to both carries and runouts. Royal Portrush is a demanding test off the tee - many holes dogleg or feature either partly or fully blind lines of attack, each of which is carefully accounted for in the players yardage book.
We'll use the signature Par 4 5th hole as our example here. It doglegs to the right meaning players can't see the majority of the landing area but given the fact it measures only 372 yards and plays both downhill and typically down wind, it's driveable for most of the field. However, not everyone will take the green on and will therefore have to pick a line off the tee to layup.
In the image below you'll see multiple lines moving horizontally across the fairway - these face the angle of the tee box. The first line on the fairway has 262 (A) written on the far side of the fairway - this in the run out yardage and is marked by a letter.
The 5th fairway with attack angles documented in red lines across the fairway
The next line has a (1) 222 written at the bottom, this is the cover yardage for players trying to cut the corner. At the end, it reads 262 (A) - again, this is the run out yardage. Cover yardages for these angles are highlighted a number in brackets eg. (1), (2), (3) etc, with the runout highlighted by a letter eg. 262 (A), 278 (B), 294 (C).
If you look at the bottom of the page, you'll also see each angle of attack highlighted with an aiming point off the tee.
The plain course map
Given the amount of detail in this book, it's rather surprising to find an almost blank course map in the middle of the book. It features a relatively colorless course map, accompanied by a compass and a blank page above.
If you get the chance to have a look at a book from a player or a caddie, both of these pages are swamped with notes from the week. This page will essentially turn into a wind map, with the caddy documenting the wind direction and seeing how that will impact strategy for each hole.
The course map in the yardage book with red pen showing the wind direction during the second round
Given the changeability of Irish weather, this wind can switch in a matter of minutes and could make previously unreachable Par 5s gettable and vice versa. Caddies will often use this page at the very beginning of the pre-shot routine to determine the wind and plan accordingly.
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