A predictive model stating that the time to reach a target is determined by its size and distance from the starting point. In UX, this means interactive elements should be large enough and close enough to where users' attention or pointer already is.
Common contexts
- Sizing primary action buttons on mobile screens large enough to be reliably tapped with a thumb
- Placing a context menu close to where a right-click was initiated rather than at a fixed screen corner
- Designing a toolbar where frequently used tools are grouped closer to the active canvas area
Use when
When designing any interface where speed and accuracy of interaction matter — especially touch interfaces, toolbars, and navigation menus where the physical distance between elements affects task completion time.
Avoid when
Don't apply Fitts's Law in isolation to make every element large and close together — maximizing target size while ignoring visual hierarchy and spacing creates cluttered layouts that are harder to scan, not easier to use.
Fitts's Law is most violated not in button sizing but in confirmation dialogs — placing 'Cancel' next to 'Delete' at the same size and proximity is a design error that causes real data loss in production every day.
Real-world examples
- Apple's macOS places the menu bar at the very top edge of the screen—making it an infinite-height target per Fitts's Law—so the cursor stops at the screen edge, speeding up menu access.
- Microsoft's Windows Taskbar and the macOS Dock are positioned at screen edges, exploiting Fitts's Law to make frequently used application launchers faster to click than centered alternatives.
- Google's mobile search button is designed to be large and thumb-reachable on mobile screens, applying Fitts's Law to reduce the time and error rate for the most frequent user action.