I’ve talked about Fitts’ Law before. But I wanted to create a very concise definition here, so that we can discuss things in meetings.

Fitts’ Law

Fitts’ Law is a model to account for the time it takes to point at something, based on the size and distance of the target object. Fitts’ Law and variations of it are used to model the time it takes to use a mouse and other input devices to click on objects on a screen.

Broadly, Fitts’ Law can be applied by designers to suggest moving target buttons closer and making them larger for extremely commonly used buttons. In detail, applying the formula can be extremely useful for exact design of time-critical applications.


T = k log2(D/S + 0.5), k ~ 100 msec.

T = time to move the hand to a target
D = distance between hand and target
S = size of target