Fitts's Law

Fitts's Law is an empirical model of human rapid aimed movement, predicting that movement time increases logarithmically with the ratio of distance to target size. Formulated by Paul Fitts in 1954, this fundamental law describes how long it takes to move to and select a target (e.g., clicking a button on a screen or reaching a physical object). In human-computer interaction, Fitts's Law is widely applied to evaluate and optimize pointer-based interfaces such as mice, touchpads, and touch screens.