More than three-quarters of all PCs running Windows 8 or 8.1 will migrate to Windows 10 in the first 18 months of the latter's lifecycle. A smaller percentage of Windows 7 PCs will add hundreds of millions more to the tally, even though most business and government devices will not shift to Windows 10 until 2017 or later.
The calculations are based on the performance of Windows 8.1, the free upgrade Microsoft shipped in October 2013 as the follow-up to the original Windows 8 of the year before.
According to analytics vendor Net Applications, which measures operating system user share by tracking unique visitors to its customers' websites, 76% of PCs running Windows 8.1 or Windows 8 ran the former in April, an increase of about 11 percentage points from six months before and 26 points compared to 12 months prior.
Windows 8.1's adoption has been unprecedented for a Microsoft OS -- not a shock since it was also the company's first free upgrade available to all users of Windows 8.
Microsoft is counting on the same trend for Windows 10: Two weeks ago, the company publicly set a goal of having the new OS running on one billion devices within two to three years. To meet that target, analysts have calculated, Windows 10 will not only have to capture virtually the entire consumer new PC market during the 24-to-36-month stretch and power a larger number of smartphones, but also convince a significant chunk of Windows 7 users to upgrade to 10, either by purchasing a new device or taking advantage of Microsoft's free upgrade offer.
With Windows 8.1 as a guide -- and the fact that Windows 10 is also free -- it's a good bet that 76% of the former at the time the latter launches will be upgraded within 18 months. In other words, if Microsoft launches Windows 10 in July, it should be able to get three-fourths of all Windows 8 and 8.1 PCs (as of that month) onto the new OS by the end of 2016.
Assuming 1.52 billion Windows PCs worldwide, that translates into 198 million machines (17.1% share for Windows 8/8.1 at the end of June x 76% = 13% x 1.52 billion).
Figuring Windows 7's migration is more problematic. Research firm IDC says that approximately 55% of all PCs are in the hands of consumers, 45% in commercial organizations. If that ratio applies to Windows 7 -- which will account for 67% of all Windows PCs by June's end -- that means consumers' systems will represent about 37% of all Windows 7-powered machines.