The last time Microsoft made a global Windows claim was in May 2013 when Julie Larson-Green, who then led Windows development, said there were 1.4 billion Windows PCs.
Allowing for the intervening nine months -- and the fact that most new systems are not additive, but replacements for older machines discarded or retired -- assume that there are now approximately 1.5 billion Windows devices in use.
In fact, the 1.5 billion matches the number IDC analyst Rajani Singh has pegged of "active devices, fully operational PCs, and not those that are placed in the attic or closet," a figure she said in an email included pirated or non-paid Windows licenses.
Net Applications' staked Windows 8's user share for January at 11.66% of the computers running one edition or another of Windows. Multiply that by 1.5 billion and one gets:
11.66% x 1.5 billion = 174.93 million Windows 8 devices
To check the validity of Net Applications' user share numbers and in-use hardware, one can call up a Dec. 6, 2011, Microsoft claim that there were then 1.25 billion Windows PCs. Alongside the 1.25 billion data point, Antoine Leblond, a vice president of Windows Web services, said Microsoft had sold 500 million licenses for Windows 7.
Microsoft's claimed it has sold 200 million Windows 8 licenses, marked by the red bar at the left. The others are various estimates of actually-in-use machines. (Data: Microsoft, Net Applications, StatCounter, IDC, Benedict Evans.) Click on graph to enlarge.
According to Net Applications, at the end of November 2011, Windows 7 powered 37.51% of all Windows devices. So ...
37.51% x 1.25 billion = 468.94 million
Another way to generate an estimate of the number of Windows 8 devices is to use Windows 8's user share of all computers. There, Net Applications put the OS's number at 10.58%. (Windows 8's share of all computers is smaller than its share of Windows-only devices because the latter accounts for about 91% of the whole.)
Estimates for the installed base of all in-use personal computers range from 1.6 billion (by Benedict Evans, now an analyst with venture capital firm Andreessen Horowitz) to 1.63 billion (Gartner, last fall, in a take on the number likely to be in place by the end of 2013) to 1.74 billion (IDC's Singh).
10.58% x 1.6 billion = 169.28 million
10.58% x 1.63 billion = 172.45 million
10.58% x 1.74 billion = 184.09 million
So, the estimates for Windows 8 active devices ranges from a low of 169.3 million to a high of 184 million -- out of the 200 million licenses Reller claimed -- with the 175.9 million based on the 1.5 billion Windows PCs about in the middle of the range.
Sign up for Computerworld eNewsletters.