Kirk Koenigsbauer, the corporate vice president for the Office 365 Client Apps and Services team, revealed in a blog post that Microsoft believes that 10.1 inches is the dividing line between a "personal" and "professional" experience. Pros need the reliability and security of paid apps, while "personal" users are more interested in free.
"Currently, we are also using screen size to delineate between professional and personal use," Koenigsbauer wrote. "Based on our research, we are classifying anything with a screen size of 10.1 inches or less as a true mobile device: You're probably using it on the go, when it's not practical to use a larger computing device such as a PC or a Mac. You probably aren't using a mouse or a keyboard, instead navigating via touch interface. It's probably not a "pro" category tablet that is used for design or presentations."
On these mobile devices, the core editing and viewing experience will be free, Koenigsbauer wrote, until you get to those "premium, subscription features," like integration from one app to another, security, and reliability--all part of the Office 365 suite, and not the individual apps.
Why this matters: Everyone understands what differentiates a desktop from a phone. But as the lines between phones, tablets, and phablets blur, software vendors have to make a decision: What does the software experience look like as the screens they're displayed on grow and shrink At Microsoft, that dividing line will be about the dimensions of the Surface Pro tablet: 10.1 inches. And given that Microsoft's definition of "professional" doesn't include anything under 10.1 inches, that's game over for a small-screen Surface Pro tablet.
Note though, that Microsoft hasn't said anything about actually creating documents on smaller screens. So you won't necessarily be able to launch a new Office document on a small-screen tablet, just edit one you've already created. It's just another of these annoying, lawyerly distinctions that are a legacy of the old Microsoft.
Surface Pro versus Surface (Personal)
The Surface Pro 3 measures 12 inches on the diagonal; the Surface Pro 2, 10.6 inches. (The Surface 2 also measures 10.6 inches on the diagonal, but it's been essentially discontinued.) With Microsoft's new definition of screen size as the divider between "personal" and "professional" use, it seems to imply two things concerning the Surface and Surface Pro lines.
First, any hopes of a small-screen Surface Pro mini are effectively dashed. Jan Dawson, principal at Jackdaw Research, said that we might still see a non-Pro Surface model--AKA the Surface 3--at less than 10.1 inches, however.
Microsoft had yet to answer requests for comment by publication time.
In any case, Koenigsbauer said that Microsoft will continue to push its free individual apps, such as Word, PowerPoint, Outlook, Skype, and others, to third-party hardware makers, as Microsoft did Monday. The company partnered with Samsung, Dell, and others to bring Office and Office 365 to Android tablets.
Office for iOS has been downloaded more than 80 million times already, Koenigsbauer said. Office 365 Home and Office 365 Personal grew to more than 9.2 million subscribers in the last quarter, up 30 percent, he said. And as Microsoft continues to push its apps across the whole of the computing ecosystem, that number will continue to grow.