How Miller’s 7±2 Law Can Boost Your App’s Usability

American cognitive psychologist George A. Miller published the seminal 1956 paper “The Magical Number Seven, Plus or Minus Two” in *Psychological Review*, providing one of the earliest quantitative studies of short‑term memory. The article notes a coincidence between the limits of one‑dimensional absolute judgment and short‑term memory capacity, both hovering around the number seven.

In short‑term memory, people can retain on average 7 (±2) items; that is, a set of roughly seven items can be remembered as a whole.

Applying Miller’s law to everyday interface design can enhance product usability:

1. Reduce user choices to avoid choice overload

When designing a product, eliminate unnecessary options and keep the number of selectable items low. For example, the WeChat Reading app displays at most nine books on a shelf, and iOS folders show a maximum of nine apps.

In mobile apps, bottom navigation bars typically contain 3‑5 items; exceeding five can lead to mis‑taps due to limited screen space.

2. Distinguish hierarchy and group similar information

If an app has many functional entry points, display no more than ten on the home screen (the tenth often labeled “All” or “More” to access the next level). Prioritize important functions, place secondary ones in sub‑levels, and use visual cues—larger color blocks, prominent icons—for the top five, while de‑emphasizing less‑used items.

3. Chunk long information to reduce memory load and streamline actions

When users must input long strings such as phone numbers, bank cards, or ID numbers, break them into smaller blocks for easier verification. For address entry, let users select larger regions first and only type the specific building number. Apps like Taobao provide smart auto‑fill to further reduce effort.

Miller’s law inspires many more design tactics; combining theory with practice helps designers attend to subtle details. For further reading on related design theories, see the linked article.