Fitts’ Law in 2 Minutes
Tags: User Experience, User Experience Design, UX, UX Research, User Interface

Fitts’ Law in 2 Minutes

What is Fitts’ Law

To be honest, Fitts’ Law isn’t really a law at all. It’s actually a descriptive model of human psychomotor behavior that’s written as an equation like this one.

Fitt’s Law.

In the formula, MT is the average time to complete the movement. A&B are model parameters. D is the distance of movement from start to target center. W is the width of the target. Fitts’ Law is a model of human activity. It monitors the time it takes, taking into account the target’s size and distance to point at something.

However, this seems super complicated so far; the Rule of Fitts is easy-to-understand.

Fundamentally, it demonstrates that hitting bigger targets closer to you is quicker than hitting smaller targets that are further away from you. If you look at the keys on your computer keyboard, you’ll notice that the keys users press most often: the enter key, the space bar, and the shift key are larger than the other modifying keys.

Photo by Troy Chen on Unsplash

These keys are more extensive, so they’re easier to hit. They’re also closer to the alphanumeric keys. Keys that are used less often like: insert, delete, and escape are farther away from the alphanumeric keys.

User experience designers use Fitts’ Law when creating user interfaces. Good UX designers ensure that they make it obvious any time they want users to interact with the software or the interface. Targets are easily located and easy to use. UX designers also know that the farther away a user’s mouse is, and the smaller the on-screen target is, the longer it takes someone to move the cursor and click on the target.

We know that the size of the target matters.

The larger the target, the easier it is to hit.

This might lead a designer to think that the more oversized buttons are always better. However, that isn’t still the case. Fitts’ Law is a curve, which means that smaller objects are more comfortable to click if they’re made larger. However, larger items are already large, so they aren’t any easier to connect if they’re made larger. Because of this curve, the benefits of increased size begin to decrease.

Designers! This is good news for us because it frees up more on-screen real estate and ensures on-screen objects are appropriately sized for their intended use. Good on-screen target placement is critical. As a UX designer, the physical locations of your screen elements are essential.

The Gutenberg diagram shows that users tend to move through screens from top-left to bottom-right. Therefore, consider placing what’s important — like the buttons that call users to action, in the bottom right-hand corner.

When designing an on-screen layout, ask yourself if your critical icons are the ones users are most likely to use?

Are they on the path that your users’ cursor takes?

Remember to apply Fitts’ Law to your design principles. When designing graphics, text, and screen icons, always consider their sizes.

Are they appropriately sized for their intended use?

Consider making any text labels into links. Try making the whole phrase a link rather than just one word. This makes the target more prominent and easier for the user to hit. Keep in mind the device that your customers are using. If you’re developing a touch screen interface, ask yourself: are the elements big enough and spaced correctly to allow your user to pick just one?

The spacing between on-screen elements is just as important as the size of the elements.

Remember Fitts’ Law: it’s faster to hit larger targets closer to you than to hit smaller targets farther from you.