Your putting stroke path on a skeleton model
Even when you try to take the putter straight back, your body is built to rotate around the spine. Enter your height, arm length and putter length: the tool works out your posture with the left eye over the ball, then shows in 3D how the head moves when you move your shoulders. You can also compare the path seen from directly above with the backswing as your own eye sees it.
Set-up
Stroke
Taken back 20.0 cm, the head is on the target line (straight)
- Face angle (from above)still square to the target line
- At the end of the follow-throughon the target line (straight)
- Path at impactstraight down the target line
- Attack angle at impact0.5° up
- Head rises by1.5 cm
- Distance the head travels20.1 cm
- Body motion neededshoulder turn 6.6°, side bend 6.8°
- Shouldersleft shoulder down 2.8 cm, right shoulder up 2.8 cm
Your upper back is tilted 44° forward, so just turning the shoulders around the spine swings the head inside and opens the face. To go straight back as seen from above, you must add a side bend (tilting the shoulders up and down) of about 1/tan(44°) times the turn — enough to stand the plane up by 46°.
- Turn only
- Shaft plane
- Straight
A 20.0 cm backswing seen from above looks like 20.7 cm when your eye reads it against marks on the ground (a difference of 0.7 cm).
Seen from the eye, the top edge of the head sits above the ground, so it appears shifted slightly away from the point under your eye (parallax). The head also rises in the backswing, so the bigger the backswing, the bigger the gap. The shape of the path — straight or arcing inside — hardly changes. Grid numbers are centimetres from the face position at address.
| Shoulder motion | Off the target line | Face open | Turn | Side bend | Path at impact |
|---|---|---|---|---|---|
| Turn onlyplane 44° | -2.5 cm | 8.3° | 11.6° | 0.0° | 2.8° in-to-out |
| Shaft planeplane 70° | -0.5 cm | 3.3° | 8.6° | 4.1° | 0.2° out-to-in |
| Straightplane 90° | 0 | 0.0° | 6.6° | 6.8° | 0° |
Negative = inside. Turn is rotation around the spine; side bend tilts the shoulders up and down. With a different build (spine tilt), the same "turn only" goes inside by a different amount. Uneven shoulders lean the "turn only" axis sideways: in-to-out with a conventional grip, towards out-to-in when cross-handed.
- Forward tiltupper back 44° (lower back 29°)
- Shoulder heightright shoulder 4.6 cm lower (tilt 11°)
- Left eye height127 cm
- Elbow bend70°
- Hands28.1 cm inside the ball, 73.0 cm high
The stroke from a skeleton’s point of view
The shoulders turn around the spine
Your shoulders and arms hang from the rib cage, and the rib cage rotates around the spine. At address you lean forward, so that axis leans too. Rotating around a tilted axis makes the head trace an arc seen from above, moving inside both going back and going through. If all you do is turn your shoulders, the stroke is not straight in skeletal terms, however straight it feels.
Going straight needs side bend
For a straight-back path seen from above, the axis of rotation has to be horizontal, pointing from you to the ball. That means mixing a side bend — lead shoulder down, trail shoulder up — into the turn. The more upright you stand, the larger the share of side bend you need. Golfers who bend over more get close to straight with a turn alone.
Swinging along the shaft is the middle ground
The shaft leans at the lie angle (about 70°). Swinging in that plane gives a gentle inside-to-inside arc of around 5 mm at 20 cm back, with the face square to the path and about 3° open to the target line. Many good putters are said to sit around here.
The low-hand shoulder drops (conventional vs cross-handed)
One hand sits below the other on the grip, so the shoulder on the low-hand side drops a little. With a conventional grip (right hand low for a right-hander) the trail shoulder ends up 4–5 cm lower and the spine axis leans slightly back. Turning around that axis brings the head in low from the inside and out through the ball: an in-to-out bias. Cross-handed, the lead shoulder is the low one and the axis leans the other way, so the same turn drifts towards out-to-in. That change in shoulder height is why the stroke feels different when you switch to cross-handed.
How it compares with measured tour strokes
In SAM PuttLab data from 99 PGA Tour players on 4 m putts, the face rotated 3.2° on average through the 20 cm around impact, and most players swung on an arc that goes inside on both sides of the ball. “Shaft plane” in this tool gives 3.3° per 20 cm, almost the same. “Turn only” gives about 8°, more than double what was measured. Good putters are evidently not just turning the shoulders: they mix in side bend and swing close to the plane of the shaft. Their average attack angle was 2.8° upward, close to what the model gives with the ball about 5 cm ahead of the lead eye.
Your eye sees the backswing a little longer
With the left eye over the ball, the view from above and the view from your eye are almost the same. But the top of the head is 2–3 cm above the ground and rises as you take it back, so against marks on the ground it looks a little longer than it is: about 7 mm at 20 cm and about 3 cm at 40 cm. Worth knowing when you practise backswing lengths against markers.
Assumptions and sources
Segment lengths come from ratios to body height (Winter’s anthropometric table); only arm length can be entered. Shoulder joints are 0.2 × height apart, the hip joints sit at 0.5 × height with the knees slightly flexed and the ankles almost directly below them (0.03 × height ahead), and the back is split into a lower and an upper part, with the upper part rounded 15° more than the lower. The default elbow bend is 70°, matching a putting set-up with the elbows tucked to the sides.
The address posture is solved from three conditions: the left eye over the ball (or where you set it), both hands on the grip (centred 10 cm below the butt), and the elbows bent by the angle you enter. Real set-ups vary, so treat the posture numbers as a guide.
The stroke is modelled as shoulders, arms, hands and putter rotating as one unit around a single axis through the centre of the shoulders (a pendulum with quiet wrists and elbows). The head and lower body stay still. The axis is set by the plane you pick under “How the shoulders move”; turn and side bend are that axis split into the spine direction and the chest direction.
Shoulder tilt is set to half of the tilt that would let both arms reach the grip at equal length (the other half is assumed to be taken up by a difference in elbow bend). The upper back is assumed to lean towards the low shoulder by a quarter of that tilt, and the “Turn only” axis includes this lean. These shares are assumptions, not measurements, so treat the in-to-out amount of “Turn only” as a guide. Left-handed is the right-handed calculation mirrored. Moving the ball towards the target moves the whole body back by the same amount.
The eye view is a perspective view from the eye position at address. Backswing length is read where the line of sight through the top edge of the head (face side) meets the ground. Depth perception with two eyes, eye movement and head rotation are not included.
- D. A. Winter, Biomechanics and Motor Control of Human Movement, 4th ed. (Wiley, 2009) — segment lengths as a fraction of height
- C. Marquardt, “The SAM PuttLab: Concept and PGA Tour Data”, Annual Review of Golf Coaching 2007 — 99 PGA Tour players, 4 m putts
- J. Karlsen, G. Smith, J. Nilsson, “The stroke has only a minor influence on direction consistency in golf putting among elite players”, J. Sports Sci. 26 (2008)
- J. Karlsen, Performance in golf putting (doctoral thesis, Norwegian School of Sport Sciences, 2010)
About this tool
“Straight back and straight through” is common putting advice, but the body is built to rotate around the spine, and when you lean over the ball a shoulder turn alone moves the head on an arc. This tool builds a skeleton-like model of your set-up from your height, arms and putter, works out the head path for different ways of moving the shoulders, and shows both your natural path and the body motion it takes to make it straight.
Posture worked out for your build
From your arm and putter length, it finds the posture that puts the left eye over the ball with both hands on the grip. With the same putter, taller players bend over more and shorter players stand more upright.
Three shoulder motions side by side
“Turn only”, “Shaft plane” and “Straight” are drawn on top of each other, with a table of how far each goes inside, how much the face opens, and how much turn and side bend each needs.
View from above and from your eye
The view from directly above and the view from your eye at address are drawn at the same scale, so you can see how much longer your backswing looks when you judge it by eye.
FAQ
Straight back or inside-to-inside: which is better?
Either rolls the ball the same way if the face points at the target at impact. Research on elite players found that most of their directional scatter comes from the face angle, with the path playing a minor part. A practical approach is to find the plane your build swings in naturally, then work on matching the face.
Why does “Turn only” go so far inside?
Turning only around the spine moves the head in a plane tilted like your spine. In a real stroke most people mix in some side bend without thinking, so their path falls between “Turn only” and “Straight”. Measurements of 99 PGA Tour players also show face rotation close to the “Shaft plane” value. Use the table to see both ends for your build.
What changes if I putt cross-handed?
The lead hand goes low, so the lead shoulder drops and the shoulder line tilts the opposite way to a conventional grip. In a turn-only stroke, conventional leans in-to-out and cross-handed leans towards out-to-in. Switch “Grip” to compare shoulder height and the path at impact.
How do I measure my arm length?
Hold your arm out level to the side and measure from the bony point at the top of the shoulder (the acromion) to the wrist crease. If unsure, leave “Estimate from height” on.
Related articles
- Can you really take the putter straight back? The stroke path your skeleton allows, checked against tour data
- How to make your putting distance more consistent: measure your spread as a percentage, then remove the causes one by one
- Choosing the right putter: blade vs mallet, by stroke, build and personality
- Putting distance control comes from stroke length: double the backswing, four times the distance