What it measures
At impact two directions matter: where the clubhead is traveling and where the face is pointing. Together they form a flat plane, called the D plane. The ball's spin axis sits at right angles to that plane, so when the plane leans, the spin axis tilts and the ball curves.
D Plane Tilt is how far that plane leans from straight up and down, in degrees. It uses the same sign rule as Spin Axis: positive points to a curve right and negative to a curve left. When face and path match, the plane is vertical and the tilt is zero. It is calculated from face angle, dynamic loft, club path and attack angle, and leaves out the effects of off-center strikes, so it reflects the delivery only, while Spin Axis reflects what the ball actually did.
Typical numbers
There are no standard tour averages for this metric. Because it is essentially the delivery-only version of Spin Axis, typical values follow the same pattern: skilled players stay within a few degrees of zero for stock shots, and the same Face to Path produces more tilt with a driver than with a wedge.
The size of the gap between D Plane Tilt and Spin Axis is often more useful than the number itself. With irons the two are usually close. With drivers they can differ by several degrees or more on off-center strikes.
What changes it
Face to Path is the main input: the larger the difference between face and path, the more the plane tilts. Spin loft controls how sensitive it is. With low spin loft, like a driver hit slightly up, a small Face to Path tilts the plane a lot; with high spin loft, like a wedge, the same Face to Path tilts it much less. Strike location does not change it, by design.
What it changes
D Plane Tilt does not change the ball by itself; it predicts the curve your delivery should produce. Comparing it with Spin Axis tells you what happened at contact. If Spin Axis is more to the left than D Plane Tilt, a toe strike likely added draw spin; more to the right suggests a heel strike added fade spin.
How to use it
Use it to decide whether to work on your swing or your strike. If D Plane Tilt already matches the shape you see, change face or path. If it says one thing and the ball does another, work on hitting the center of the face first.
Bay drill: with a driver, hit ten shots and note D Plane Tilt and Spin Axis for each. Mark any shot where they differ by more than about 3 degrees and check the impact mark. Then tee the ball slightly lower or higher, or stand slightly closer or farther, and see if the gap shrinks.