Defining Mobile: 4-5.5 Inches, Portrait & One-Thumb

by Luke Wroblewski April 28, 2015

The word mobile has come to mean many things. But when designing mobile software, we need some clarity. What kind of devices are we talking about and how do people interact with them?

Looking at ScientiaMobile’s report on 5.2 billion Web requests from the end of 2014 gives some answers. Globally, smartphone penetration is close to or over 60% on all continents. Feature phones, where still used (Africa 7% , South America 8%), are continuing to decline.

Average Smartphone Diagonal

67% of smartphones range between 4 and 5.5 inches and 94% of the time they’re used in portrait orientation. Note this data is based on Web browsing but native app numbers are unlikely to change the majority of use to landscape.

Average Smartphone Orientation

When in landscape mode, most interactions (72%) rely on just one thumb as Steven Hoober's 1,300+ observations of smartphones in use illustrated.

Common Postures

So when designing for mobile today, it’s worth considering a 4-5.5 inch smartphone, in portrait (vertical) orientation, being used with one-thumb. Of course, there many variants as well but making sure your mobile experiences work well in this context is a great baseline to start from.

Defining Mobile

A few examples of how this baseline can inform design decisions and testing:

  1. Designing for Thumb Flow
  2. Testing One-Thumb Mobile Use