Putt stroke simulator
Enter the length and period of the stroke, the face angle and path at impact, and where on the face you strike it. The collision between head and ball is computed, and from that how far the ball rolls.
- Start direction
- Face angle
- Swing path
- Target line
- This stroke
- Centred and square
Distance（m）
Left/right (cm) ← left right →
Show the figures as a table
| Distance | Left/right | Speed |
|---|---|---|
| 0.00 m | 0.0 cm | 2.56 m/s |
| 0.74 m | 0.0 cm | 1.80 m/s |
| 1.46 m | 0.0 cm | 1.55 m/s |
| 2.07 m | 0.0 cm | 1.31 m/s |
| 2.58 m | 0.0 cm | 1.06 m/s |
| 2.99 m | 0.0 cm | 0.82 m/s |
| 3.28 m | 0.0 cm | 0.56 m/s |
| 3.46 m | 0.0 cm | 0.29 m/s |
| 3.53 m | 0.0 cm | 0.02 m/s |
| 3.53 m | 0.0 cm | 0.01 m/s |
Roll distance（m）
Backswing length (cm)
Show the figures as a table
| Backswing length (cm) | Roll distance |
|---|---|
| 5.0 cm | 0.09 m |
| 7.5 cm | 0.21 m |
| 10.0 cm | 0.37 m |
| 12.5 cm | 0.59 m |
| 15.0 cm | 0.86 m |
| 17.5 cm | 1.18 m |
| 20.0 cm | 1.55 m |
| 22.5 cm | 1.97 m |
| 25.0 cm | 2.44 m |
| 27.5 cm | 2.96 m |
| 30.0 cm | 3.53 m |
| 32.5 cm | 4.15 m |
| 35.0 cm | 4.83 m |
| 37.5 cm | 5.54 m |
| 40.0 cm | 6.32 m |
| 42.5 cm | 7.13 m |
| 45.0 cm | 8.00 m |
| 47.5 cm | 8.93 m |
| 50.0 cm | 9.89 m |
| 52.5 cm | 10.91 m |
| 55.0 cm | 11.98 m |
| 57.5 cm | 13.10 m |
| 60.0 cm | 14.24 m |
- Face angle
- Swing path
- Current setting
Finishing position left/right (cm) + = right
Angle (°) + = right
Show the figures as a table
| Angle (°) + = right | Face angle | Swing path |
|---|---|---|
| −5.0° | −25.6 cm | −4.9 cm |
| −4.5° | −23.1 cm | −4.5 cm |
| −4.0° | −20.5 cm | −4.0 cm |
| −3.5° | −18.0 cm | −3.5 cm |
| −3.0° | −15.4 cm | −3.0 cm |
| −2.5° | −12.9 cm | −2.5 cm |
| −2.0° | −10.3 cm | −2.0 cm |
| −1.5° | −7.7 cm | −1.5 cm |
| −1.0° | −5.2 cm | −1.0 cm |
| −0.5° | −2.6 cm | −0.5 cm |
| 0.0° | 0.0 cm | 0.0 cm |
| +0.5° | +2.6 cm | +0.5 cm |
| +1.0° | +5.2 cm | +1.0 cm |
| +1.5° | +7.7 cm | +1.5 cm |
| +2.0° | +10.3 cm | +2.0 cm |
| +2.5° | +12.9 cm | +2.5 cm |
| +3.0° | +15.4 cm | +3.0 cm |
| +3.5° | +18.0 cm | +3.5 cm |
| +4.0° | +20.5 cm | +4.0 cm |
| +4.5° | +23.1 cm | +4.5 cm |
| +5.0° | +25.6 cm | +4.9 cm |
- Distance
- Left/right (+ = right)
- Current setting
Difference from a centred strike (cm)
Strike point (mm) − heel toe +
Show the figures as a table
| Strike point (mm) − heel toe + | Distance | Left/right (+ = right) |
|---|---|---|
| −25 mm | −41.2 cm | −3.0 cm |
| −23 mm | −34.3 cm | −2.8 cm |
| −20 mm | −26.9 cm | −2.5 cm |
| −18 mm | −20.9 cm | −2.3 cm |
| −15 mm | −16.4 cm | −2.0 cm |
| −13 mm | −11.6 cm | −1.7 cm |
| −10 mm | −7.8 cm | −1.3 cm |
| −8 mm | −3.9 cm | −1.0 cm |
| −5 mm | −2.3 cm | −0.7 cm |
| −3 mm | −0.6 cm | −0.3 cm |
| 0 mm | 0.0 cm | 0.0 cm |
| +3 mm | −0.6 cm | +0.3 cm |
| +5 mm | −2.3 cm | +0.7 cm |
| +8 mm | −3.9 cm | +1.0 cm |
| +10 mm | −7.8 cm | +1.3 cm |
| +13 mm | −11.6 cm | +1.7 cm |
| +15 mm | −16.4 cm | +2.0 cm |
| +18 mm | −20.9 cm | +2.3 cm |
| +20 mm | −26.9 cm | +2.5 cm |
| +23 mm | −34.3 cm | +2.8 cm |
| +25 mm | −41.2 cm | +3.0 cm |
- Head and ball are treated as rigid bodies and the collision, with friction, is solved in three dimensions. During impact the head is taken to be free of any force from the shaft or the hands. The turn of the face while the head twists during the roughly 0.9 ms of contact is included.
- The stroke is modelled as simple motion. The pendulum is simple harmonic motion striking at the lowest point; "accelerating" is constant acceleration from the top of the backswing to impact.
- The figures for each putter type are guides. Moment of inertia is a typical catalogue value and centre of gravity depth is estimated from the head shape; neither is the figure for a particular model.
- The part of the sidespin that is about the vertical axis does not change the velocity of the point touching the ground, so it has no effect on the roll. But the spin axis is always at right angles to the direction the ball leaves in, so it is tilted relative to the ground by the launch angle, which leaves a small component about the direction of travel (sidespin × tan of the launch angle). That component produces sideways friction while the ball lands and skids, and it is included in the roll (usually one to a few millimetres).
- The sideways push and the sidespin from an off-centre strike come from one and the same impulse. That puts a ceiling on how much the spin can bring the ball back: even if the spin axis pointed fully along the direction of travel, it would only cancel most of the push. The ball does not curve back across the target line. Raising "share of sidespin that acts on the roll" lets you explore up to that ceiling.
- An off-centre strike really does twist the head (about 1° for a blade struck half an inch off centre, which agrees with measurement). But the ball is on the face for a little under a millisecond, and in that time the face turns by less than 0.1°. Most of the twist happens after the ball has gone. What changes the ball’s direction is the face sliding sideways as the head twists.
- Both the loss of ball speed on an off-centre strike (about 4% at 20 mm) and the direction error (0.034° per mm on average across 10 putters on a pendulum rig) agree with published measurements. Magazine and manufacturer figures two or three times larger exist, but they are close to treating the twist angle itself (about 1°) as the ball’s direction, and this model does not reproduce them.
- A right-handed player is assumed. Strikes high or low on the face, shaft flex and fine undulations in the green are not included.
How to read and use this simulator
Head speed is worked out from the length and period of the stroke; then the collision between head and ball, the skid and the roll are computed in turn to find where the ball stops. There is no hole. The tool is for moving one input at a time to see how far a given stroke rolls the ball and how much each error costs.
Control distance with stroke length
Double the backswing at the same period and head speed doubles, so the ball rolls about four times as far. With the defaults (30 cm backswing, 1.2 s period, Stimp 9.5, flat) the ball rolls about 3.5 m; a 20 cm backswing gives about 1.6 m and 40 cm about 6.3 m. Hold the rhythm steady and change only the length, and distance becomes much easier to judge.
Change the rhythm and the distance changes too
With the same 30 cm backswing, shortening the period from 1.2 s to 1.0 s stretches about 3.5 m to about 5.1 m; lengthening it to 1.4 s cuts it to about 2.6 m. This is why putts tend to run long when nerves quicken the stroke.
Direction is set almost entirely by the face
Open the face by 1° and the ball starts about 0.83° right; swing the path 1° to the right and it starts only about 0.17° right. At 3.5 m that is about 5 cm for the face against about 1 cm for the path. To cut down directional misses, check the face angle before the path.
Miss the sweet spot and distance goes first
With a blade, striking 10 mm towards the toe leaves a 3.5 m putt about 8 cm short and about 1 cm right. At 20 mm it is about 27 cm short. A large mallet with a high moment of inertia loses about 13 cm for the same 20 mm. Switch putter type under the Putter tab to compare.
Frequently asked questions
The distance does not match what I get on the green
The stroke is reduced to a simple motion. Real strokes differ from player to player in the pause at the top and in how they accelerate. Switch the stroke type, set the period to your own rhythm and the Stimp value to the green of the day, and the figures move closer. For what remains, use ratios rather than absolute values: how many times farther the ball goes when the backswing is 1.5 times as long.
How do I measure my own period?
Film the stroke in slow motion on a phone, time it from the top of the backswing to impact, and multiply by four. In a pendulum motion, top to impact is a quarter of the period, so 0.3 s means a period of 1.2 s. The top-to-impact time for the current period is also shown under the input.
Why does a toe strike start right and a heel strike start left?
An off-centre strike twists the head, and the face, which sits in front of the centre of gravity, moves sideways and pushes the ball (the gear effect). The amount is small: about 0.2–0.3° for a 10 mm miss. What stands out in an off-centre strike is the lost distance rather than the direction.
Does sidespin make the ball curve part-way along?
In the calculation, hardly at all. Sidespin on a putt is about a nearly vertical axis, which does not change the velocity of the point touching the ground. The axis tilts by the launch angle, so the effect is not zero, but in most cases it is one to a few millimetres. Almost all of the left-right difference between strike points comes from the difference in starting direction.
With a large mallet, does an off-centre strike stop mattering?
The distance loss shrinks, but the direction error does not. Direction error is roughly proportional to centre of gravity depth divided by moment of inertia, and a large mallet has a deeper centre of gravity as well as a higher moment of inertia. With the guide figures used here, a 20 mm miss finishes about 2.5 cm offline with a blade and about 3.5 cm with a large mallet.
What do loft and angle of attack affect?
The launch angle and how far the ball skids before it starts rolling. With 3° of loft and a level strike the ball launches about 2.5° upwards and skids for roughly the first 0.6 m of a 3.5 m putt. The effect on distance is small: going from 0° to 6° of loft changes it by about 8 cm.
Can left-handers use it?
Yes. Read a positive input as open, or towards the toe, enter the side slope the opposite way round from the real one, and swap left and right in the results.