Laws of UX, 2nd Edition

Chapter 2. Fitts’s Law

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

Key Takeaways

• Touch targets should be large enough for users to accurately select them.
• Touch targets should have ample spacing between them.
• Touch targets should be placed in areas of an interface that allow them to be easily acquired.

Overview

Usability is a key aspect of good design. It implies ease of use, which means the interface should be easy for users to understand and navigate. Interaction should be painless and straightforward, requiring minimal effort. The time it takes for users to move to and engage with an interactive object is a critical metric. It’s important that designers size and position interactive objects appropriately to ensure they are easily selectable and meet user expectations with regard to the selectable region—a challenge compounded by the differing precision of the range of input methods available today (mouse, finger, etc.) and the variable dexterity of users.

To aid in this endeavor, we can apply Fitts’s law, which states that the time it takes for a user to engage with an object is relative to its size and the distance to it. In other words, as the size of an object increases, the time to select it goes down. Additionally, the time to select an object decreases as the distance that a user must move to select it decreases. The opposite ...