Clearly defining the business and consumer markets has been a key strategy of Microsoft’s freemium approach to Office. The company is taking it a step further now as any device with a screen size of 10.1 inches or less is considered a mobile device which means Office’s core editing and viewing features will come free of charge.

Kirk Koenigsbauer, corporate vice president for the Office 365 Client Apps and Services team, said in a blog post that since the Office for iPad announcement last March, they have spent a lot of time considering the use cases and business implications involved in bringing Office to different platforms.

Devices with screen sizes of 10.1 inches or less are probably used on the go where it’s not practical to use a larger computer, he said. Such a device likely also lacks a mouse and keyboard and thus, isn’t categorized as a “pro” tablet used for design or presentations.

Offering a free core experience exposes more people to Microsoft’s productivity suite and thus far, the strategy has been paying off. Koenigsbauer said Office for iOS has been downloaded more than 80 million times in less than a year, a statistic that has also led to a 30 percent uptick in subscriptions to Office 365 Home and Office 365 Personal. Another impressive statistic – one in seven people use Office every day.

It's worth pointing out that the classification also all but eliminates the possibility of a small-screen Surface Pro mini (although Microsoft seems to have made that decision long ago).