Deep dive: laying out a mobile lander around the thumb, not the screen

Deep dive: laying out a mobile lander around the thumb, not the screen

Desktop layout thinks in eyes; mobile layout must think in thumbs. The ergonomic research here is Steven Hoober's field observation work (thousands of people observed holding phones in the wild) plus Scott Hurff's thumb-zone mapping: most one-handed users hold the phone and reach with the thumb, creating an arc of easy reach, a band of stretch, and corners that are genuinely hard to hit. Your conversion element belongs in the easy arc.

The layout playbook:

— Step 1: Map the zones. On a typical right-handed grip, the natural arc covers the lower-center and lower-right; the top corners are the strain zone. Treat the bottom third as premium real estate.
— Step 2: Anchor the primary call-to-action in the thumb arc. A sticky bottom button stays in the easy zone through the whole scroll — far better than a single button stranded mid-page.
— Step 3: Size touch targets honestly. Platform guidelines converge near a ~44–48px minimum; smaller targets raise mis-tap rate, and a mis-tap is friction plus frustration.
— Step 4: Space targets apart. Adjacent tappable elements cause fat-finger errors; padding between them is not decoration, it's accuracy.
— Step 5: Keep destructive or wrong actions out of the arc. If "cancel" sits where the thumb rests, you'll harvest accidental exits.
— Step 6: Test one-handed, walking. Lab conditions (two hands, sitting, full attention) hide the errors real mobile use produces.

Mechanism: on mobile, the cost of an action isn't just cognitive, it's physical. A button in the strain zone adds literal effort, and effort suppresses action at the margin where conversions are won or lost.

The caveat: grips vary — left-handed, two-handed, and cradle holds all differ. You can't optimize for one perfectly. The robust move is the bottom-anchored, full-width or center-weighted button, which is reachable across the common grips rather than ideal for one.

TL;DR
— Map the thumb arc; treat the bottom third as premium and anchor the call-to-action there (sticky).
— Touch targets ~44–48px minimum with real spacing; keep wrong actions out of the arc.
— Optimize for grip variety with a bottom-anchored button, and test one-handed.