User eXperience

Hick's Law, what is and what is its formula

Hick's Law is not some kind of weird disease you get when you can't stop hiccuping, but if you're looking for a cure, you won't find it here. 😜

So, what is Hick's Law?

It's a fancy way of saying that the more choices you have, the longer it takes to make a decision. It's like when you're in a restaurant with a menu that's 50 pages long, and it takes you an hour just to decide what to order.

But don't worry, there's a solution! Just apply Hick's Law to your design and simplify your choices. It's like when you're at a restaurant with a one-page menu, and you can make a decision in under a minute. That's what we call efficient design!

This is a universal mathematical formula that allows calculating the time required to make a decision, defined as Reaction Time (RT).

Hick's formula

RT = a + b log2(n)

In this formula, "n" represents the number of choices or stimuli, "a + b" are the constants, or the conditions under which choices are made, and "RT" is the reaction time, or the time taken to make a choice.

Basically, Hick's Law states that:

"the time it takes a person to make a decision is proportional to the entropy of the decision, that is, the amount and complexity of existing alternatives."

How to apply HIck's Law to design

How many times have you started a project and your stakeholders have a million features and pages in mind, which you end up piling up haphazardly in a navigation menu due to haste?

In design, Hick's Law is applied - albeit almost unconsciously - to effectively examine how many features to offer the user and in which parts of the site.

I don't know if you've ever heard of that experiment with jam sales at a stand, which says something like:

Customers at a stand were more likely to buy jam jars when there were only SIX flavors on display compared to when there were TWENTY-FOUR, because making a decision when there were too many flavors discouraged potential buyers, leading them to choose nothing and therefore not buy anything.

The application of this law is actually simple: reduce the number of choices and stimuli so that your "customers", or users, make choices more quickly.

However, beware that Hick's Law only applies in situations where there are simple choices to make.

In fact, in the case of choices that require a certain degree of attention or concentration, such as the multiple-choice questions on a university test, Hick's Law cannot be considered valid.

As we all know, time is precious for everyone, so the faster the choice, especially when it comes to navigation in an e-commerce or a dashboard or a SaaS, the more your product's User eXperience will benefit.


There are exceptions, which are excellently explained in a short video by NN/g that I propose below.

1. Ordered list

Even a list of 40/50 items can be easy to use, even easier than a list containing only 10 items, but there are conditions to be met.

The menu or list must contain the items in a specific order, such as alphabetical order, as in the example of Google Translate below:

Google Translate ling list o language in the mega menu
Google translate list

Giving order to the list, such as the alphabetical order of the list of languages on Google Translate.Google Translate languages listAs you can well imagine, knowing that the list has a certain order, our eye will have no trouble finding what it is looking for, even though there are over 120 available languages.

Imagine how much fun it would be if they were in random order! 🙂

2. The user must know the meaning

The user must also know the meaning of the words and have a certain confidence in what is written.

As in the list of languages on Google Translate mentioned above, if you are looking for the Polish language (for example), it will always and only have that name, and there will not be another word replacing it.

The user is thus able to easily identify the word, even within a long list.

...and what if the law cannot be applied?

There are cases, which hopefully are rare, where it is difficult to give the user few options, either due to the complex nature of the product being designed or due to the huge amount of information that needs to be provided.

A simple solution is to create categorizations.

In fact, a categorization exercise is very important because it not only allows you to create groups that have the same meaning, but above all, it makes it easier for the user to find what they are looking for.

But don't forget to use categorizations that are understandable to your users, otherwise the exercise becomes useless.

A simple and effective exercise that is often done in UX Research in these cases is card sorting.