Card sorting: The three steps of three

An easy technique for sorting cards with subjects into seven themed piles.

A technique of three easy steps to sort any number of cards/subjects into seven thematic groups. The Card sorting technique is used in Information Architecture as a tool for planning eg. sections of a web site. This article will show you how you can end up with seven groups in all cases.
Published here on November 11, 2004. Copyright: © 2004 Claus Schmidt,
Citations (quotes, not full-text copy) are considered fair use if accompanied by author name and a link to this web site or page.

Website navigation: A pile of cards

If you've ever planned or rearranged a website (or made directory-type site maps) you have probably met the standard rule-of-thumb stating that:

...there should be no more than seven main groups in the navigation...

Let's not discuss this rule here. In stead, let's just face the fact that for a website, this implies only seven main topics. Personally I've been working with small web sites as well as very large ones, and regardless of size it's more-or-less always the case that: If there's more than eight pages on the site there's more than seven subjects (front page always counts as one extra page).

When working with very large sites, ie. the portal kind, it is not uncommon that the number of "logical groups" on the site is a double digit number. Still, it is always possible to arrange the information in just seven groups. Below, I'll show you how to do it in just three steps.

I call this technique "the three steps of three". Feel free to use the name, as it contains all the steps required in it, just don't pretend you coined it.

Here we go:

The starting point: You have too many groups

Of course you have been doing this the proper way: You've noted all the subjects on the site on individual small pieces of paper, and hence made a "deck of cards". Then you've used the best of your skills in semantics to arrange this deck into reasonably homogenous piles. You've even bended some rules and definitions to make some groups a bit larger, all in order to get the total count of piles as small as possible. Still, you end up with 18 piles and not the seven you aimed for.

This is where we start. Now, take a deep breath, because after spending all that time arranging cards in neat piles and reshuffling over and over again, what you have to do now will not be easy, and it will not seem logical either. Don't worry, we'll get there eventually.

Ready? Now, take your 18 piles and forget about all the time it took to get there. Just make one big pile out of them, and forget about the order of those cards totally. Shuffle them around so there's no order to them, if you please. Back to square one, that is.

Step one: Make three groups

If you've read the headline, you've probably guessed it. Take that big pile of cards and make no more than three groups out of it. Not four, not seven, not 18. Three. And no more.

Yes, three is a very low number, I know - still, it can be done. What you want to do here, is to identify the two broadest possible groups and "the rest". Try to get as much as possible in one of the two broad groups and as little as possible in the "rest" group. The result of your effort will be these three groups:

  1. Group a
  2. Group b
  3. "the rest"

If it turns out that "the rest" is a larger group than one of the other two, you should choose another topic/headline for the smallest one and re-sort the whole deck of cards. Your target should be to get the "rest" group as small as possible.

When you have two very large groups and one very small group, step one is done. Unless you can do another round to make the "rest" group even smaller.

Step two: Make three groups again

Now, can you find a common name for the "rest" group? No? Thought so. That's allright though.

Your new task is to do exactly the same with group one and group two. Forget about "the rest" for now. After you've sorted group one and group two into three sub-groups you will have:

  1. Group a, topic A
  2. Group a, topic B
  3. Group a, "the rest"
  4. Group b, topic C
  5. Group b, topic D
  6. Group b, "the rest"
  7. "the rest"

See? You've got topic A,B,C,D now. It looks as though you've got seven groups as well, but three of them are not very intuitive, as they're basically residual groups.

Step three: Make three groups and end

Now, forget about A,B,C,D for a while. Take (3), (6), and (7) from the list above and make one big group out of it. Guess what? Sort that pile into just three groups: Topic E, topic F, and "the rest" - doing exactly the same things as before.

When you're done with that you'll have:

  1. Group a, topic A
  2. Group a, topic B
  3. Group b, topic C
  4. Group b, topic D
  5. Group c, topic E
  6. Group c, topic F
  7. "the rest"

Now, for completeness sake, take another round with group (7), but this time around don't split it up in three. In stead, try to fit the cards from pile (7) into the other piles. It might take a couple of rounds, but the result will be that group 7 becomes more focused.

That's it: Three steps to seven groups

Easy, isn't it? And all you have to think about at each step is to make just three groups: Two that are as broad as possible, and a residual group that is as small as possible. For sub-navigation, all you have to do is this: Take groups 1-7 and make three groups out of each. Not four, not seven, not 18. Just three.