In 2019 the Rules of Golf stopped penalizing a putt that hits the flagstick (Rule 13.2a). Is the pin a backstop or an obstacle? Golf Digest asked Cal Poly engineer Tom Mase to find out.
Each putt below starts 2.5 feet out and is paced to roll 4.5 feet past if it misses, matching his test. Hit one to watch it in slow motion, or run a thousand and watch the make rate fill in across the cup.
| Flagstick | Putts | Holed, all lines | Holed, glancing | Mase, glancing |
|---|
- All lines
- every simulated putt, aimed anywhere across the cup.
- Glancing
- only putts whose line clips the side of the stick (with the pin out, the same lines with nothing in the way). This is what Mase tested.
- Mase
- his real result for those putts, 90 per stick at 4.5 ft of pace.
Model tuning
Pin settings apply to the selected stick and clear its results. Lip and limit settings apply to all sticks.
- Cup view: drag to orbit. A single putt slows to ⅕ speed around the cup so you can see the contact; batches play at real speed. Each miss is labeled: lipped out, over the back edge, or off the stick.
- Chart: the cup as the ball sees it. Each dot is a putt, holed (top) or missed (bottom), at the point it crossed the cup.
- Bars and table: “glancing” means putts whose line clips the side of the stick, the case Mase tested. Each bar is the simulator’s make rate for those putts; the red tick is Mase’s real result.
The experiment
Mase rolled putts off a Perfect Putter ramp set 2.5 feet from the hole, so every putt left at the same speed. He varied:
- The flagstick: none, fiberglass, tapered aluminum, dual-diameter aluminum.
- Contact: dead center, or a glancing blow off the side.
- Pace: enough to roll 2.5, 4.5, 8, 9, or 10+ feet past if it missed. A “4.5-foot putt” means that pace, not that distance.
What he found
Dead center, the pin barely matters. Every putt dropped at 2.5, 4.5, and 8 feet of pace, pin in or out. The stick only saved putts struck hard enough to roll 9+ feet past.
Glancing blows, the pin knocks the ball out. Only about 28% of pin strikes are dead center. At 4.5 feet of pace, off-center contact:
| Flagstick | Holed |
|---|---|
| Pin out | 81/90 (90%) |
| Fiberglass | 55/90 (61%) |
| Tapered aluminum | 32/90 (36%) |
| Dual-diameter aluminum | 34/90 (38%) |
A glancing blow sends the ball sideways, the shortest way out of a 4.25-inch cup, before it has dropped far enough to stay in. Stiff aluminum kicks it harder than flexible fiberglass.
About the simulator
The ball is a 3D point ball rolling on the green. The cup’s edge is a real ring it can roll over, pivot on, and bounce off, which is what flings a lipped-out putt across the hole. Three things are tuned to Mase’s data: how much a rolling ball’s topspin makes it climb the back lip (so dead-center putts pop out at 9+ feet of pace with the pin out, as he saw), and each stick’s diameter and bounce. With those set, the simulator lands within a few points of his glancing-blow results for all four setups.
Where 99.9% comes from
The pin helps only on a dead-center hit (about 28% of pin strikes) from a putt struck to roll 9+ feet past (under 1% of putts). Multiply those out and the stick saves roughly one putt in a thousand.
A separate test with college golfers found no real difference in distance control with the pin in, though players putted a bit more boldly with it.
Verdict
Pull the flagstick. Dead-center putts drop either way. Glancing ones drop about half as often with the stick in.
Sources
- Golf Digest. “The science behind why the flagstick should be pulled 99.9 percent of the time.” Golf Digest · Australian Golf Digest reprint
- USGA and R&A. The Rules of Golf (2019), Rule 13.2a: the flagstick. USGA (PDF)