Search Handbook Cards

The law assumes rapid aimed movement; slow tracking and dragging are outside its scope

The law covers movement time, not target search or deciding where to click

Coefficients must be calibrated for device, limb, and population

“Bigger buttons are always better” ignores finite layout area

The law describes an average trend, not one operation

Pointing time is jointly determined by target distance and width

Enlarging a target and shortening travel have different costs

Treating index of difficulty as a single quality score is misuse

Area and bubble cursors enlarge activation without changing visual target size

The minimum touch-target size is set by fingertip contact area, not vision

Edges and corners have unbounded width in the direction of movement

Two-dimensional targets require both width and height; minimum-edge and projected-width models differ

The hit target may be larger than the visual area

Hit area, not visual size, determines difficulty when they differ

A too-small chevron on a split button misses into the menu

Enlarging a target primarily shortens correction, not the ballistic phase

Distance and width affect time logarithmically, not linearly

Do not place destructive actions on an accidental-activation path

Approach angle changes effective width, so the same button differs by direction

Width is the effective size along the movement direction

Corners are bounded in two dimensions and have the lowest cost

Touch and full-screen system gestures weaken the effect

Proportional error reduction per correction yields a logarithmic time relation

A law's ordering of alternatives is more credible than its absolute value

Pointing usually comprises a fast ballistic stroke and slower corrections

A predicted difference smaller than individual variation is not design evidence

Adding group-average predictions amplifies rather than cancels error

Time in a constrained channel is determined by its length and width

Parallel operations cannot be estimated by adding time

Laws calibrated under separate conditions double-count preparation and response when added

Widening a channel or allowing departure lowers cost

Diagonal movement in cascading menus is a typical constrained channel

A dialog's close button can be engineered to be hard to hit

Row height trades viewport comparison against how hard a row is to hit

Zooming makes effective target width variable

On large phones the top bar sits in a hard-to-reach zone

The time cost of zooming itself must be counted

Without visual feedback, correction cannot occur and movement becomes ballistic

Path planning across zooming and panning affects total time

Edges are unbounded in the direction of motion, so pointing cost is lowest

Elongated targets are easier along the long axis than the short axis

Corners are cheapest but hold almost no targets

In an infinitely zoomable space, time grows with relative index difference, not absolute scale

Fitts' law models movement time as a logarithmic relation to target distance and width

A mobile primary often fills the width to make reaching easier

Not to be confused with the logarithmic pointing law — the applicable conditions differ

Finger size sets a lower bound on effective width

Once a target is smaller than the fingertip, gains from enlargement diminish

Selecting small distant targets is extremely hard

A touchscreen has no cursor, so endpoint error cannot be corrected mid-flight