The number one question I get asked when teaching information architecture is how many items can I have in the top level of my global navigation? It’s a good question. We know that having too many menu items can be overwhelming users and cause them to not read the options. Conversely, too few options make for vague categories that don’t have strong information sent. They don’t give a clear guidance as to what you might find within them.
A common misconception is that you should have no more than seven items in your navigations top tier. And this is a misunderstanding of the classic research study by George Miller called the magical number seven plus or minus two. So in this 1956 paper, he wrote about his research into human working memory and discovered that people could on average only keep between five and nine items in their short term memory. Hence seven plus or minus two users aren’t forced to memorize the items in your menus. They’re available right there in front of them to read. So I’ll repeat it because it bears repeating the magical number seven does not apply to navigation menus. OK, so is there a rule of thumb? Well, to use the most popular you phrase of all time, it depends. It depends on these four factors. First, how broad the scope of your content is in e commerce. Big box store that sells a huge range of products will always need more menu options then really focus site that only sells one thing like t shirts. Second, it depends how well the text labels describe the content and how succinct they are. The language you use matters a lot here. If the categories are clearly named and they’re mutually exclusive, then a larger number of categories can be used without overwhelming users. Third, it matters whether users are looking for something specific, a known item when they come to the site or if they’re browsing with more fuzzy goals in mind. If users are engaged in no nineham searching, you can often have fewer categories with a deeper structure. It also matters how well prioritize the items are. If the most common or popular items are placed at the beginning and at the end, they’re easier to spot rather than in the middle where they can get kind of lost. So many with ten or more top level items that are clearly described can be much more usable than this plague of websites with only three items that I see all the time, like products, services and about us at the top level. And that’s it. These are not descriptive. That could be any website.
Organize your content in logical buckets, then name those clearly that will advertise what you offer on your site.