What is Fitt’s Law?
A model of human movement predicts that the time needed to move to a target varies with the distance to and size of the target. The purpose of Fitts' law is to help in the study and comparison of input devices. It has been verified to be able to predict user performance in certain common tasks, such as point-selection and point-dragging tasks using common input devices like a mouse, trackball, or stylus.
Fitts' law states that the time required for a person to move a pointer (eg, mouse cursor) to the target area is a function of the distance to the target divided by the size of the target. Thus, the longer the range and the smaller the target size, the longer it will take.
Fitts' law applies widely in UIUX design. It is a predictive model for the speed of human motion, commonly used in human-computer interaction. It states that the time it takes a person to select an object depends on how far they are from the object and the size of the object.
The law applies to sharp, pointed movements, not to constant motion (eg, drawing). Such movements usually have a large motion component (ballistic movement), followed by fine adjustments to achieve the target.