What is Miller's Law?
In 1956 the psychologist George A. Miller published “The Magical Number Seven, Plus or Minus Two”, reviewing experiments on how much information people can process and remember at once. Across very different tasks, the limit hovered around seven items.
Later work refined the number: Nelson Cowan argued in 2001 that, once people can't rehearse or group items, the real capacity is closer to four chunks. Either way the message is the same — working memory is small.
Chunking: the practical side of Miller's Law
A chunk is a meaningful unit. “4915 2034 7781” is easier to remember than “491520347781” although the digits are identical. Websites use chunking all the time:
- Group form fields under short headings (“Contact”, “Delivery”, “Payment”).
- Split long articles with descriptive subheadings and short paragraphs.
- Format codes, phone numbers and IBANs in small blocks.
- Break long lists into categories, and long processes into numbered steps.
- Limit comparison tables to the attributes that matter for the decision.
The “seven menu items” myth
Miller studied what people remember. Navigation menus stay visible on the screen, so visitors don't need to memorise them — they recognise options. Cutting a useful menu to exactly seven items because of Miller's Law is a misreading; Hick's Law (decision time) and clear grouping are better guides for menus.
Where Miller's Law does apply is when people must hold information while doing something else: comparing plans across a page, remembering a code from one step to the next, or keeping track of what they configured earlier.
Lensux finds the largest list-style groups on each page and flags those with more than 9 items, so you can split them into labelled sub-groups.
Frequently asked questions
Is the magical number seven still valid?
The idea of a limited short-term memory is solid, but the exact number varies with the material and task. Modern estimates are closer to four chunks.
How do I apply Miller's Law to a form?
Group fields into small sections with clear headings, ask only for what you need, and show multi-step progress so people don't have to remember earlier answers.