Universal Principles of Design, Updated and Expanded Third Edition

069 Fitts’ Law

The time required to touch a target is a function of the target size and the distance to the target.

Fitts’ law, proposed by the psychologist Paul Fitts, states that close, large targets can be accessed more quickly and with fewer errors than distant, small targets. In addition, the faster the required movement and the smaller the target, the greater the error rate due to a speed-accuracy tradeoff. Fitts’ law has implications for the design of controls, control layouts, and any device that facilitates movement to a target.1

Fitts’ law is applicable for rapid, pointing movements, as opposed to more continuous movements, such as writing or drawing. Pointing movements typically consist of:

1. A ballistic movement — One large, quick ...