Predicting the efficiency of interaction techniques can be crucial for designing user interfaces. While models like Fitts’ law make general predictions, there is little research on how efficiency varies under different conditions like in which screen region a movement starts and in which direction it is going, and whether the surface is horizontal or vertical. This study investigates these aspects with regard to translation movements on a touch screen, using an extended Fitts’ law setup and considering arm kinematics. The results show that on horizontal displays translation is faster and causes less arm fatigue than on vertical ones. Also, on horizontal displays, we identified screen regions and movement directions that allow significantly faster movement compared to others. Finally, movements that employ shorter kinematic chains (e.g. just the wrist) are significantly faster than those that use longer ones (e.g. wrist, elbow, shoulder). We suggest adjustments to Fitts’ original formulation. In the future, our findings can inform or partially automate positioning decisions in interaction design.