Fitts’s law

This was new one to me.

It states that:

The farther you are and the smaller the target, the longer it takes to move the cursor and point at said target.

Tom Stafford said it best:

“Although the basic message is obvious (big things are easier to select) it is the precise mathematical characterization that is exciting, and that this characterization includes a logarithmic function – which means that the shape of the relationship between size and reaction time is curved so that small increases in size for small objects make it much easier to select them (whereas small increases in size for big objects don’t make that much difference). And the same applies for changes in target distance.”

Size and selection times: Fitts’s Law


or in maths speak    MT = a + b log2(2A/W)


I came across this rule in the this post The Opposite of Fitts’ Law by Jeff Atwood



Where he talks about not putting the the “Delete Forever” button too close to the “Save” button. Just like you would what to put the Ejector seat switch next to radio


More info on Fitts’s Law