30 · Doing
Fitts's Law
How long it takes to hit a target depends on how far away it is and how big it is.
Evidence: Holds upWhat we do with it
- 01
Measure the hit area, not the drawing. A 16-pixel icon can sit inside a 44-point button.
- 02
On a desktop, screen edges and corners are the easiest targets, because the pointer can't overshoot them. On a phone, the easiest spot is wherever the thumb already rests.
- 03
Make destructive actions harder to hit by accident: smaller, farther from the main action, and undoable.
- 04
The numbers to check against: Apple asks for 44 by 44 points, Google for 48, and the WCAG 2.2 floor is 24 pixels.
Examples
Getting it wrong, getting it right.
Don't
A 16-pixel close icon in the corner of a mobile pop-up.
Do
A 44-point close button, or tap anywhere outside to dismiss.
Don't
Delete right next to Save, the same size and color.
Do
Save where the thumb already rests. Delete smaller, set apart, and undoable.
The evidence
What the research says.
Among the most repeated results in human-computer interaction, precise enough to write into a standard. Scott MacKenzie's 1992 version is the one used to test pointing devices, and his 2004 review with William Soukoreff of 27 years of Fitts' law work in HCI backs the method in the ISO 9241-9 standard for testing them. A screen edge shows the law at work: the cursor stops there, so a menu bar on the top edge is in effect endlessly tall.
Sources
- Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6).
- MacKenzie, I. S. (1992). Fitts' law as a research and design tool in human-computer interaction. Human-Computer Interaction, 7(1).
- Soukoreff, R. W., & MacKenzie, I. S. (2004). Towards a standard for pointing device evaluation, perspectives on 27 years of Fitts' law research in HCI. International Journal of Human-Computer Studies, 61(6).
Last reviewed November 7, 2026. How we keep this current