The latest count of Windows 10 devices was just shared at Microsoft’s Ignite conference:

http://www.seattletimes.com/business/microsoft/microsoft-says-400-million-devices-using-windows-10/

ATLANTA — Microsoft says there are 400 million devices running Windows 10, the operating system the company released in July 2015.  That’s up from 350 million in June.  The updated figure, timed to the start of Microsoft’s Ignite information technology worker conference, is the first update since the company backed off the timeline for its goal to get 1 billion devices using the new operating system.

Windows 10 was designed to give users a similar look and feel on devices from laptops to tablets and smartphones. The original usage goals for the operating system includied assumptions about smartphone sales that proved overly optimistic after Microsoft sharply curtailed the smartphone hardware business it bought from Nokia in 2014.