Should you putt with the pin out or the pin in?

There are few changes in the modern game of golf that have generated so much discussion, occasional absolute conviction, and possible persistent indecision as the 2019 rule allowing players to putt with the flagstick left in the hole. Prior to this, striking the unattended pin with your ball from on the putting green resulted in a two-stroke penalty (or loss of hole in match play).

The 2019 change has certainly altered amateur golf. We now have some players preferring to put with the pin in. Some absolutely insist on this, even when the ferrule is worn and the pin is lying asymmetrically and even when the wind is blowing and the pin is oscillating wildly. Others prefer the pin out. Again some absolutely insist on it. Some like the pin in for long putts but out for short ones. Some like the pin out except when putting downhill. It’s all very difficult!

Rather than being a rule change that speeded up play, rather it seems to slow it down while a sort of golfing hokey cokey goes on.

Put the pin in,

Pull the pin out,

In, out, in, out,

Shake it all about……

What was once a matter of etiquette and routine has become a question of preference.

However the decision about putting pin in or pin out is really a problem in applied physics: a question of speed and velocity, of energy, momentum, elastic properties and crucially of geometry. And like many such questions in golf, the answer depends rather less on certainty, than on how one chooses to weigh the competing uncertainties in the various physical parameters, that you cannot actually know – but can only estimate!

The underlying physics is not in dispute. When a golf ball strikes the flagstick, part of its kinetic energy is dissipated through deformation and friction. A centrally struck flagstick can act as a partial barrier, reducing the speed of a ball that might otherwise have raced past the hole. In that narrow sense, the flagstick can increase the likelihood that a firmly struck putt is retained rather than lost.

This was the essence of the work associated with Dave Pelz (a former NASA physicist and famous golfer teacher) whose experiments demonstrated that, under very controlled (and arguably contrived) conditions, more putts could be holed when the flagstick was left in than when it was removed. The mechanism is straightforward and physically sound. Here is an article that he wrote in 2019 arguing that the science (or at least his experiments) suggested you putt with the pin in.

However, the transition from laboratory or mechanical putting devices to real greens introduces a complication that is less often stated plainly: golf balls do not, in practice, strike the flagstick in a perfectly central and repeatable manner. Entry angles vary, strike quality varies, the properties of the flagstick and its angle vary and green conditions introduce further irregularity. It is here that later work by Tom Mase (professor of mechanical engineering at California Polytechnic State University) shifts the emphasis. The key question becomes not “what happens if the ball hits the flagstick well?”, but “how often does that favourable geometry actually occur?” Here is an article reporting his studies that suggest you putt with the pin out. His studies might be viewed as more relevant to the real golfing world.

So in regard of the question how often does that favourable geometry actually occur the answer in realistic conditions, appears to be: not as often as one might hope! This is really important! Off-centre impacts are very common. In those cases, the flagstick can act not as a helpful buffer ( as argued by Pelz), but as a deflecting obstacle. Balls that would otherwise have dropped on a glancing trajectory may be diverted away from the centre of the cup. In statistical terms, the distribution of outcomes matters more than the best-case scenario.

This distinction explains much of the apparent disagreement in the literature.

• Pelz’s work identifies a real physical advantage under some very specific impact conditions that are arguably simplistic.
• Mase’s analysis challenges the assumption that those conditions dominate in actual play and emphasised the geometry of the situation and the distribution of outcomes.

Both are, in their own terms, correct; they are simply answering different questions. Pelz was concerned with conditional physics, while Mase focused on the probabilistic reality that is both more realistic and relevant.

Reviewing the evidence the Golf Digest commentator Mike Stachura wrote

Leaving the flagstick in may have some benefits but from a physics standpoint, there is zero evidence to suggest that the flagstick helps in any but the rarest of situations.

What is perhaps more revealing than either sets of experimental result is the behaviour of elite golfers and in particular professionals. If the flagstick conferred a clear and consistent advantage, one might expect a rapid convergence of practice. And indeed that is the case: but not in favour of leaving the pin in! Watch elite golf and it is very very rare to see any putt taken with the pin in! I’ve watched a lot of golf in the last few weeks including play from The Scottish Open, The Ladies Evian Major, The Open and this week the Scottish Senior Open and The Ladies Scottish Open. Many professionals put with the pin in on long putts where the principle aim is to lag close to the hole. In contrast only one player, Charlie Hull, consistently putts with the pin in for long and short shots.

This pattern is not easily dismissed as mere habit. Professional golf is highly sensitive to marginal gains, and players are generally quick to adopt changes that yield even small but reliable advantages. The persistence and prevalence of pin-out putting in effectively all makeable situations suggests that any benefit from leaving the flagstick in is, at best, very modest and certainly context-dependent. Indeed one professional golfer recently quipped “the only thing I want to see in the hole is my ball!”

In the amateur game there is a lot more variation in strategy. The practical conclusion, then, is less dramatic than the early Pelz versus Mase rhetoric implied. There is no universal approach that the flagstick should always be in or always be out. Rather, there are distinct regimes of play and different players will have different perspectives. On longer putts, the visual of the pin as a target may be useful. On fast downhill putts where speed control is uncertain, the flagstick may offer a slight safety net against excessive pace. On shorter putts, where precision dominates and unintended deflections carry greater relative cost, removal remains the more conservative and logical choice: but not everyone agrees.

The science, properly understood, does not deliver a single prescription. It describes a set of interacting effects whose net outcome depends on geometry, speed, and frequency of occurrence.

In the end, golf rarely rewards theoretical and abstract purity. It rewards repeatable performance under imperfect conditions. On that basis, the flagstick is neither universally an aid nor a hindrance. It is a variable, and like many variables in the game, its value is situational.

Or, more plainly: the decision about the pin (in or out) is more nuanced. The best option for the pin is neither always in nor always out. Perhaps pin out is the more logical option for putting under most circumstances, but maybe there are situations where pin in possibly makes sense! Arguably the rigid approach that some amateurs espouse ( I always want it in…. I always want it out) is the least logical, defensible or sensible stance.

“It all depends”, as one friend quipped, “on the putt in front of you, not the argument behind you”.

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Postscript: There is one clear situation where putting with the pin in always makes sense. A friend has significant macular degeneration and significantly impaired vision. For him the new rule is a godsend as it makes it very much easier for him to putt.

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