The cognitive finding that the average person can hold approximately 7 (±2) items in working memory at one time. In interface design, Miller's Law supports chunking related information into digestible groups, limiting navigation items, and avoiding screens that demand users track too many things simultaneously.
Common contexts
- Chunking a twelve-step setup wizard into three labeled phases to reduce the perceived complexity of the overall process
- Grouping navigation links into five categories instead of displaying all fourteen top-level items simultaneously
- Redesigning a data entry form that asks users to cross-reference multiple open screens at once by combining the information on one page
Use when
Apply Miller's Law when designing interfaces that ask users to hold information across multiple steps or screens — reduce active memory demands by surfacing relevant context at the point of need rather than expecting users to remember it.
Avoid when
Don't use '7 ± 2' as a hard rule for navigation items or list lengths — modern research suggests working memory capacity is closer to 4 items, and context matters far more than any specific number.
Miller's Law is misapplied more often than it's applied correctly — the goal is to reduce active memory demands, not to hit a specific item count.
Real-world examples
- The original iPhone dock held 4 app icons and Apple still caps it at 4 — a deliberate nod to Miller's working-memory research, keeping frequently-used apps retrievable without cognitive scanning.
- Credit card fields split 16 digits into four groups of 4, exploiting Miller's chunking principle to make numbers easier to verify at a glance than an unbroken 16-digit string.
- A Google study of autocomplete drop-downs found that showing 5 suggestions outperformed both 3 and 10 in task-completion speed — aligning with Miller's observed working-memory sweet spot.