Size (W)
02 / 10
Bigger Is Faster
Increase W and pointing time drops — fast. The biggest, most-used controls should be the largest controls. The CTA isn't ornament; size is function.
Width vs. acquisition time
Distance (D)
03 / 10
Closer Is Faster
Distance increases pointing time logarithmically — meaning the cost of moving across a screen is real. Place the next action near the last one. Don't make the user travel.
Distance vs. acquisition time
Trade-off
04 / 10
The Worst Case
Small AND far is the slowest possible combination. Most accidental clicks happen here — a tiny "close" icon at the opposite corner of the screen from where the eye and pointer already are.
Size × distance matrix
Edge target
05 / 10
Edges Are Infinite
The cursor can't move past a screen edge, so any target placed against the edge effectively has infinite width along that axis. The Mac menu bar is faster than every dropdown in Windows for exactly this reason.
Slam into the edge
Corner
06 / 10
Corners Are Magic
A corner is infinite in two dimensions. The cursor slams to a stop in both axes regardless of overshoot. Start menus, close buttons, and macOS Hot Corners exploit this — the fastest possible click on the screen.
Infinite in two axes
Radial
07 / 10
Radial & Pie Menus
A circular menu places all options at the same distance from the cursor — and the slice's angular width becomes effective target size. Mature users can build muscle memory for direction, not destination.
Equal D for every option
Padding
08 / 10
Hover Buffers
A small icon can have a much larger invisible hit area. Extending the clickable region with padding makes the visual element tidy and the actual target generous — a free Fitts's-Law upgrade.
Visual ≠ hit area
Touch
09 / 10
Mobile Touch Targets
On touchscreens, the "cursor" is a finger pad — roughly 9–10mm wide. Apple recommends 44pt minimum, Material 48dp. Below that and accidental taps spike; the fastest UI becomes the most frustrating.
44 pt minimum
Steering
10 / 10
The Tunneling Effect
Moving the cursor through a narrow corridor (cascading submenus, nested context menus) is dramatically slower than hitting an open target — the steering law extends Fitts's into paths. Slipping out of the tunnel resets the user.
Cascading menu = narrow tunnel
✦
Fitts’s Law in the Age of AI
Conversational and predictive interfaces change the geometry — sometimes there is no target to point at; sometimes the target comes to you.
✦ AI Era
Conversational Input Removes the Target
When you type or speak a request, there’s no button to aim for. Distance and size stop mattering — the "target" becomes language, not a pixel region.
✦ AI Era
AI Anticipates the Next Click
Predictive UIs surface the likely next action as a large, close suggestion. It’s Fitts’s Law automated — the target travels to the cursor instead of the reverse.