// description
Fitts's Law is a predictive model of human movement stating that the time required to move to a target area is a function of the distance to the target and the size of the target. In practical terms: make important interactive elements (buttons, links, form fields) large and position them close to where the user's cursor or finger already is. Small, distant targets cause errors and frustration.
// history
Paul Fitts, an American psychologist specialising in human performance, published the law in 1954 based on experiments measuring the speed and accuracy of targeted arm movements. The law was later validated for mouse and touchscreen interactions and became a foundational principle of human-computer interaction research.
// example
A course creator with a sales page on Kajabi has a small "Enrol Now" button centred in a crowded section of the page. On mobile, it's easy to tap the wrong element or miss the button entirely. Applying Fitts's Law, she makes the button full-width on mobile, increases the touch target area, and positions it directly below the price — where the eye naturally lands after reading pricing information. Mobile conversion on the page improves significantly because the most important action is now easiest to take.
// katharyne's take
Check your most important buttons on your mobile sales page right now. If you have to hunt for the "buy" or "enrol" button, or if it's a small text link rather than a proper button, you are losing sales to physics. Fitts's Law is as close to a guaranteed conversion improvement as UX has to offer: make your most important action the easiest to take. Big button, high contrast, close to where the reader's attention already is after reading your main value proposition.
// creative uses
- Apply Fitts's Law to your Kajabi or Teachable sales page on mobile: open it on your phone right now and try to tap the enrol button with your thumb. If you miss it, misclick, or have to zoom in, that's a direct conversion loss. Make the mobile CTA button full-width with at least 48px height — the minimum tap target size recommended by Google's Material Design guidelines.
- Use Fitts's Law when designing digital product download instructions: the "download now" button in your Etsy confirmation email or Gumroad delivery page should be the largest, most prominent element on the page. If buyers have to hunt for where to get their file, you'll get support messages and low reviews for a product problem that's actually a UX problem.
- Apply it to your email CTAs: a text link saying "click here to join" is a small, hard-to-tap target on mobile. A full-width HTML button with padding is a large, easy-to-tap target. ConvertKit, Flodesk, and Mailchimp all let you add styled buttons to emails — the conversion difference between a text link and a button is measurable and consistent.
// quick actions
- Open your most important sales page on your phone and do a one-handed thumb test: can you reach and tap the buy button with your right thumb while holding the phone naturally? If not, move the button down (closer to natural thumb position) or make it full-width. Do this for every sales page you own today.
- Check your Etsy shop's "Add to Cart" button placement on mobile: on the Etsy mobile app, the add-to-cart button is fixed at the bottom of the screen — but on your own Shopify store, you control where it sits. Full-width, high-contrast, and close to the price is the Fitts's Law optimal placement.
- In your next Kajabi email or broadcast, replace every text link CTA with a styled button using a background colour, padding, and font size that make it obviously tappable. Use "Sign up now," "Join the course," or "Get instant access" rather than "click here" — the action-oriented text improves both accessibility and conversion.
// prompt ideas
Audit my sales page for Fitts's Law violations. Here's the URL or page structure: [describe your page layout and CTA placements, or paste the HTML structure]. Identify every place where an important action — buying, enrolling, downloading — requires more effort than it should on mobile, and give me specific fixes for each one.
I'm designing a sales page for [my digital product / course / Etsy listing outside page]. Using Fitts's Law alongside general conversion principles, tell me exactly where the primary CTA button should be placed, how large it should be, what colour contrast it needs, and how many times it should appear on a page of [X words / Y sections]. Give me the reasoning, not just the rules.
Review the checkout or download flow for my [Gumroad product / Kajabi course / Etsy digital download]. From a Fitts's Law perspective, where are the points of highest friction — the places where the next required action is hardest to find or tap? Give me a prioritised list of UX improvements that would reduce abandonment without requiring a platform change.