The time it takes to hit a target depends on how far away it is and how big it is. This is Fitts's Law, formalised by psychologist Paul Fitts in 1954 through controlled experiments with physical pointing tasks. The mathematical model, T = a + b × log2(2D/W), precisely predicts movement time from distance (D) and target width (W). Decades of HCI research have validated that the model applies equally to mouse movements, touch gestures, and stylus interactions. It's one of the most consistently validated principles in the field.
Fitts's Law
How target size and distance determine the speed of every interaction
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Designers Academy
2 April 2025 · 3 min read
DesignPrinciples
In brief
Fitts's Law is a principle stating that the time required to move to a target depends on the distance to the target and its size, with larger and closer targets being acquired faster.
