Why a Faraway Button Takes Longer to Reach
When you reach for a button, your brain is solving two problems at once: move your hand toward the target, then stop it accurately. A target farther from your starting point demands a longer movement. A narrow target leaves less room for error, so the hand must slow down near the end rather than simply rushing through the distance.
Fitts’s law describes this tradeoff between distance, target size, and movement time. In practical terms, reaching farther takes longer, and hitting a smaller target takes longer still. The relationship is not a conscious calculation in your head; it is a reliable pattern that appears when people make aimed movements.
Why Accuracy Changes the Movement
Your hand does not travel at one steady speed. It typically moves quickly at first, covering much of the distance, then makes smaller adjustments as it approaches the target. If the target is tiny, even a slight overshoot can miss it, so those final corrections matter more. A nearby, broad target allows a faster movement because there is more room to land successfully.
This explains why two buttons that are equally easy to see can feel different to tap. A small icon near your thumb may be easy; the same icon at the far edge of a screen may require more time and care. The difference comes from the movement the interface demands, not just from how quickly you can recognize the button.
The Design Consequence
Fitts’s law gives interface designers a practical way to predict which controls will be slow or frustrating to use. Making an important target larger or placing it closer to where a user’s hand already is can reduce the effort needed to reach it. That is especially useful on touchscreens, where fingers cover part of the display and a narrow target is easier to miss.
A small increase in target size can therefore do more than make a control look prominent: it gives the hand a wider landing zone, reducing the need for careful last-second corrections.
