TheStack Metrics Explained

TheStack works with four important metrics, which we would like to explain briefly.

Stack Speed

This is the radar measurement of the current speed without adjustments.


The stack’s shaft length is the same as that of a hybrid and is therefore shorter than that of a driver. Of course, you train for maximum speed with the driver. The eSpeed value therefore determines the club head speed with the driver and thus also takes into account the difference in shaft length.

Distance potential

Club head speed is of course an important factor to consider. The actual drive length depends mainly on your shaft, driver head and swing. It is therefore very individual. TheStack uses the app to determine a guideline for possible drive distances and makes the following assumptions:

  • 32° temperature
  • 300m above sea level
  • Total length (carry + roll)
  • Medium hard fairways
  • Neutral Angle of Attack
  • Optimised launch conditions (through proper club fitting)
  • Titleist ProV1x Golf Ball

This length potential is only shown at standard weight and not when training with light and heavy weights.

Grit Score

The Grit Score indicates how well you follow the training. If you follow the guidelines and do not skip any workouts, you will achieve a Grit Score of 100%. Any deviation from the optimum will reduce your Grit Score. This is ideal, for example, for trainers to be able to monitor the progress of their students.