That means 31 devices - including phones, laptops and Xbox games consoles - were upgraded every single second over the last 28 days.
It's the second time Microsoft has released figures indicating the success of the much anticipated Windows 10, which is a free upgrade for the many users with the previous Windows 7 and 8 OS, after the tech company said 14m devices were updated in the first 24 hours.
Windows 10, the first OS to launch under chief executive Satya Nadella, has now been downloaded in more than 192 countries, while apps in the Windows 10 store have been downloaded six times more, per device, than for Windows 8, said Microsoft's marketing vice president Yusuf Mehdi in a series of tweets.
He also said more than 90,000 unique PC or tablet models have upgraded to Windows 10 and that more than 122 years of gameplay has been streamed from Xbox One to Windows 10 devices.
Fresh from the OS launch, Microsoft is rumoured to be launching its newest version of Office on 22 September.
The reception to Windows 10 has been relatively positive, particularly for the Siri-like voice assistant Cortana which recently launched on desktop computers. Office was the only aspect of the Windows upgrade which received more negative than positive post-launch attention, according to Brandwatch.