Fitts’s law

Fitts’s Law is the principle that the time you need to hit a target depends on its size and distance. The bigger and closer the target, the faster and more reliably you click it. The smaller and further away it is, the longer it takes and the more mistakes you make. It sounds like trivial physics of movement, but in the world of websites and apps it is one of the most practical laws of UX design. It decides how easily people reach the buy button, and so it directly affects your conversions.

Classification

• Cause (Cognitive Bias Codex): The need to act fast
• Mental area: Motor skills and attention (UX)
• Marketing function: UX and conversion (CTA)
• Buyer journey: Decision and action
• Cialdini’s principles: not applicable
• System 1 / System 2: System 1 (fast, automatic)

In a nutshell

• What it is: a large, close target is hit faster and with fewer errors.
• Why it matters: an easy click on the CTA directly increases conversions.
• Where you meet it: buttons, links, forms, especially on mobile.
• How to use it: make key buttons large and place them where the thumb can reach.

A real-life story

The law was formulated by the American psychologist Paul Fitts in 1954 in a paper published in the Journal of Experimental Psychology. He originally measured movements of the human hand, but with the arrival of computers and the mouse his findings became one of the cornerstones of interface design. Today it is used every day by everyone who designs websites and apps, whether they know it or not.

Take shopping on a mobile phone. When the buy button is small and hidden in the top corner, the user stretches, misses it and gets annoyed. When it is large, high-contrast and at the bottom of the screen, where the thumb can comfortably reach, clicking takes a second. A difference of a few pixels in design can mean a significant difference in the number of completed orders. That is why apps put their main actions at the bottom and make them large, not small and at the top.

How Fitts’s Law works

Our movement towards a target always has two phases: a fast move towards the target and fine adjustment at the end. A small target needs more adjustment, so it takes longer and we miss it more easily. A large, close target needs almost no adjustment. On mobile, thumb reach is added on top, so it also matters where the button sits on the screen. The principle is linked to the Von Restorff effect, because a prominent, high-contrast button also attracts attention better, and to the default effect, where an easy path to action decides what the user does.

Use in marketing and on the web

1. Enlarge the main CTA. Make the buy or submit button large and easy to hit. Small links belong to secondary actions.
2. Think about the thumb. On mobile, place the main actions in the bottom third of the screen, where the thumb can comfortably reach.
3. Give clickable elements space. Enough spacing reduces mis-clicks, especially on touch devices.
4. Enlarge the whole clickable area. Make the entire row or card clickable, not just the small text inside it.
5. Don’t demand precision. Tiny close icons and minuscule links frustrate users. Give them a decent size.

How to work with it

1. Test on mobile. Most visits come from phones. If it works with a thumb, it works well.
2. Watch size and spacing. Keep clickable elements large enough and far enough apart.
3. Most important = largest and closest. The priority of an action should be reflected in its size and position.

How it interacts with other biases

Fitts’s Law works best paired with the Von Restorff effect. Fitts says the button should be large and within reach, Von Restorff adds that it should also stand out from its surroundings in colour. A large, high-contrast, well-placed CTA is then easy for the user to find and easy to hit. Add simplicity based on the paradox of choice and one main button per page, and you get exactly the effortlessly easy path to action that conversions are all about.

Frequently asked questions

What is Fitts’s Law?

A UX design principle stating that the time needed to hit a target depends on its size and distance. A larger, closer target is hit faster and with fewer errors.

Who created Fitts’s Law?

The American psychologist Paul Fitts in 1954. Originally for hand movements, today it is a foundation of website and app design.

How can you use Fitts’s Law on a website?

Make the main buttons large, with enough spacing, and on mobile place them within thumb reach so they are easy and quick to click.

Patrik Pilous

I am a marketing strategist and SEO consultant. I love the world of marketing, the internet and AI. I am at my best when planning business growth, setting and executing marketing strategy and optimising websites (SEO, GEO and, above all, sales).