At the end of June, exactly eleven months after its original launch, Microsoft announced that Windows 10 had made its way to over 350 million devices.
Today, at its Ignite conference - almost three months later - the company updated that figure: Windows 10 is now installed on more than 400 million devices.
Here"s how Windows 10 installations have grown since the OS launched on July 29, 2015:
| Date (official figures only) | Rolling total | Progress towards 1 billion | Days since total last updated | Average new additions per day |
| Jul 30, 2015 | 14,000,000 | 1% | 1 | 14,000,000 |
| Aug 27, 2015 | 75,000,000 | 8% | 28 | 2,180,000 |
| Oct 6, 2015 | 110,000,000 | 11% | 40 | 875,000 |
| Jan 4, 2016 | 200,000,000 | 20% | 90 | 1,000,000 |
| Mar 30, 2016 | 270,000,000 | 27% | 86 | 814,000 |
| May 5, 2016 | 300,000,000 | 30% | 36 | 833,000 |
| Jun 29, 2016 | 350,000,000 | 35% | 55 | 909,000 |
| Sep 26, 2016 | 400,000,000 | 40% | 88 | 568,000 |
Since last August, the average rate of new Windows 10 installations stabilized at around 800,000 to 900,000 per day, except around Thanksgiving and Christmas. During that period, the new OS benefited from a boost in festive sales, along with the release of the Windows 10-based "New Xbox One Experience" during the same quarter, helping to increase average daily additions to around 1,000,000.
With 88 days having passed since its last update, that means that the rate of installations has slowed considerably since Microsoft reached 350 million on June 29. From an average of 909,000 new installations (including new devices) per day, the growth rate has now decreased to around 568,000 per day - that"s still a huge number, but there"s no disguising the fact that it also represents a decline of around 38% compared with the average growth rate from May to June.
Of course, that slowdown in growth was certainly expected. Microsoft has now officially ended its free Windows 10 upgrade offer for Windows 7 and 8.1 PCs, requiring anyone wishing to upgrade to purchase a new OS license, priced from $119 (although those who use assistive technologies on their PCs can continue to upgrade free of charge for now).
But with Microsoft no longer prompting users to upgrade to the new OS via its Get Windows 10 app, we"re likely to see the growth rate remain similarly low in the weeks and months ahead.
In July, Microsoft admitted that it will miss its planned target of a billion Windows 10 devices by 2018, which it announced in April 2015. Microsoft remains confident that it will reach its one-billion goal, but said that it will take longer than its 2018 fiscal year to reach that target.