101 UX Principles – 2nd edition - Second Edition

#73

Make Tappable Areas Finger-Sized

If you think your design will be used by touch, then your users’ fingers are the tool that they’ll use. Given that obvious statement, it’s surprising to see UI controls in touch interfaces that are clearly way too small for users to poke at easily with their digits.

As a guide, your smartphone screen is (roughly) five fingers wide and 10 fingers high, so—if you introduce padding (the area around each control)—that’s about 40 controls: a hard limit of the controls that can be comfortably used on such a display. If you were to try to fit more than four or five items horizontally across the display, they would be too small to be comfortably used.

You’ll need to experiment to find the right control size, but ...