Big targets that are close are quick to hit. Small, far ones are slow.
Time to acquire a target depends on its distance and size. Bigger + closer = faster.
Pay is tiny and stuck in the far corner of a phone checkout. Drag it to where your thumb reaches and make it big enough to hit, and watch the reach and size meters answer every move.
Place primary actions in the bottom third and make them ≥44×44pt.
On a 6.7-inch phone, a “Pay” button stranded in the top-right corner forces an awkward reach and invites mis-taps. Move it to the bottom of the screen and make it full-width. Now it's a big, close target: faster to hit and far harder to miss. This one change routinely lifts mobile checkout completion.
Flip it on purpose for dangerous, irreversible actions. A “Delete account” button should be smaller and farther away, not the biggest, closest thing on screen. Here friction is a feature: the extra distance is what prevents mistakes.
Fitts's Law says the time it takes to reach a target depends on how far away it is and how big it is. Bigger and closer targets are faster to hit. It comes from a 1954 study by the psychologist Paul Fitts.
Movement time = a + b × log₂(1 + D/W), where D is the distance to the target and W is its width. The constants a and b depend on the device and the person.
A large Pay button at the bottom of a phone screen, within thumb reach, is faster to hit and harder to miss than a small one in the top corner. On a desktop, screen edges and corners are easy targets because the cursor stops at the edge.
Make primary targets large (at least 44 by 44 points on touch screens), place them where the thumb or cursor naturally rests, and keep related controls close together. Keep destructive actions small and farther from the main one.
Yes. The same trade-off between distance and size applies to a finger, but targets also need to be big enough for a fingertip. On large phones, the bottom of the screen is the easiest zone to reach.
A notes app took off on 6.7-inch phones, but 'New note' lives top-right — the one corner a thumb can't reach one-handed. Reviews are piling up about how awkward it is one-handed.
Usability bugs are easy to spot but hard to name. The right law points straight to the fix.