Fitts's Law
Big and close is easy to hit - the law that says make important buttons large and well-placed, especially for thumbs on mobile.
- Term
- Fitts's law
- States
- Time to hit a target depends on size & distance
- Implies
- Make key targets large & well-placed
- Critical for
- Buttons, tap targets, mobile
Forms & parts of speech
Definition in plain terms
Fitts's law is a principle from human-computer interaction and motor psychology stating that the time it takes to move to and acquire a target - like clicking a button or tapping a link - is a function of the target's size and its distance from the starting point.
In plain terms: larger targets and closer targets are faster and easier to hit, while small, distant targets take longer and are more error-prone. This has direct, practical implications for interface design.
Important interactive elements, like primary buttons and calls-to-action, should be made large enough to hit easily and placed where they're convenient to reach.
The principle is especially important on mobile, where people tap with imprecise thumbs and certain screen areas (like the bottom and center) are far easier to reach than others (like top corners).
Designing with Fitts's law makes interfaces faster and less frustrating to use, which directly affects whether people complete actions.
Why it matters to growth leaders
Fitts's law is a practical lever for a growth leader because the ease of hitting key targets - buttons, calls-to-action, form controls - directly affects whether people complete the actions growth depends on.
A primary call-to-action that's small, awkwardly placed, or hard to tap (especially on mobile) introduces friction and lost conversions; making it large, prominent, and easy to reach removes that friction.
On mobile in particular, where a growing share of traffic and conversions happen, Fitts's law is critical: placing important actions within easy thumb reach and sizing tap targets generously can meaningfully improve completion rates.
For a growth leader optimizing flows and pages, this is a concrete, testable design principle - ensuring the elements people need to interact with are easy to hit reduces friction and supports conversion.
It pairs with visual hierarchy (making the right thing prominent) and the broader discipline of removing every unnecessary obstacle between the visitor and the action.
On mobile, the primary checkout button is small and positioned near the top of the screen - awkward to reach with a thumb - so users have to stretch and often mis-tap, introducing friction at the most critical moment.
By Fitts's law, the time and effort to hit a target depend on its size and distance, so a small, hard-to-reach button is slow and error-prone exactly where ease matters most.
The growth leader enlarges the checkout button and moves it into the easy thumb-reach zone at the bottom of the screen, and sizes other key tap targets generously. Taps and completed checkouts rise, because the most important action is now effortless to hit.
The leader applies the principle across mobile flows - generous tap targets, primary actions within thumb reach - recognizing that on mobile, where a growing share of conversions happen, Fitts's law is decisive.
Pairing it with visual hierarchy so the right element is both prominent and easy to hit, the growth leader removes the physical friction between the visitor and the action, turning a subtle interaction obstacle into a measurable lift in conversion.
Synonyms & antonyms
Synonyms
Antonyms
Origin & history
Fitts's law relates the time to hit a target to its size and distance - bigger and closer is faster; a cornerstone of interaction design, it guides sizing and placing buttons and tap targets, especially on mobile, to reduce friction and support action.
Etymology: source.
Usage trends
Search interest for this term over the last five years:
Common questions
- What is Fitts's law?
- A principle stating that the time to move to and select a target depends on its size and distance — larger, closer targets are faster and easier to hit, which guides button and tap-target design.
- How does Fitts's law apply to conversion?
- Primary buttons and calls-to-action that are small or hard to reach introduce friction and lost conversions; making them large, prominent, and easy to hit — especially on mobile — supports completion.
- Why is Fitts's law important on mobile?
- People tap with imprecise thumbs and some screen areas are far easier to reach than others, so sizing tap targets generously and placing key actions in easy thumb reach meaningfully improves completion.
Related tools & calculators
Resources & people to follow
- referenceWikipedia — Fitts law
- referenceUX and CRO practice
- referenceRGM analysis — make key targets large and within easy reach, especially in mobile thumb zones; it removes physical friction and supports conversion
Curated, non-competitor resources verified per term.
Related training
Disciplines
Areas of marketing where fitts's law is a core concern: