Fitts Law

The size and distance of a target affects the time required to move to it

Devised by psychologist Paul Fitts in 1954, this law states that the time needed to make a single movement to a resting position over a target is influenced by the distance between the starting point and the target, and the size of the target. For example, moving a mouse pointer to rest on a large button a short distance away will take less time than moving the pointer to a smaller button at a greater distance.

Fitts’s Law has been shown to work in a wide range of conditions and using different parts of the body, for example hands, feet, eyes, and head-mounted sights. It also works with different input devices and in various physical environments.

Faster movement speeds and/or smaller targets will reduce accuracy. Designers can make targets larger or closer to decrease the time needed to move to them, but care should be taken to ensure the benefits of these changes don’t cause other usability problems.