How big are the double greens at the Old Course?

Jordan Spieth was one shot back of the lead on No. 8 tee in the final round of the 2015 British Open on the Old Course at St. Andrews, and he knocked his tee shot at the 174-yard par 3 onto the green. Normally that would be cause for at least a little satisfaction, but not necessarily on the Old Course.

That’s because most of the putting surfaces on the Old Course – which this week hosts its 30^th British Open – are gigantic double greens that serve two holes with flagsticks planted on opposite sides. As can so easily happen after an approach shot finds the wrong portion of one of these greens, Spieth faced a putt of some 100 feet. His ensuing four-putt – his first attempt sailed off the green ­– and the double-bogey 5 left him playing catchup the rest of the day, and he eventually fell one shot short of a playoff won by Zach Johnson.

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None of this is a knock on Spieth’s putting – he was a top-10 putter on the PGA Tour that year, and that double bogey clearly was caused by an errant iron shot. On a normal course, Spieth would have missed the green, likely by a wide margin, and he probably would have pitched a wedge shot of some kind onto the putting surface without ever leaving such a dent in his putting stats.

The Old Course is different, and errant iron shots don’t always lead to pitches or chips. Instead, players often face massive putts for which they must judge distance, extreme mounding and even the wind if they are to have any hope of getting their first putt close.

The Old Course has only four greens that serve just one hole, at Nos. 1, 9, 17 and 18. The rest of the holes play to one side of seven giant double greens. An interesting note for the hardcore golf nerds: If the two hole numbers served by a double green are added together, they always equal 18. For example, No. 2 and No. 16 share a green, so they equal 18. Other shared greens are Nos. 3 and 15, Nos. 4 and 14, Nos. 5 and 13, Nos. 6 and 12, Nos. 7 and 11, and Nos. 8 and 10.

And they are huge.

The average size of the putting surfaces at the Old Course is 22,267 square feet, more than half an acre, and the double green for Nos. 5 and 13 is over 37,000 square feet. By comparison, the average green size at Pebble Beach Golf Links, another seaside course famed for hosting major championships,…