About 63% of all iOS devices were running iOS 15 as of January 11th. App Store statistics for iPads are included in the data, which can be found on Apple's Developer portal on the App Store support page. Compared to the majority of iPhones that have been released in the last four years, just 72% of new iPhones run iOS 15, which is an improvement above iOS 14's install rate of 81% a year ago.
For iPads, 57% of devices that are at least four years old are running the latest version of the operating system. All iPads are running the current version of the operating system, which is iPadOS 14, at 37%. According to Apple, it is now possible to obtain the most recent security updates if a user does not have to update to the most recent OS version.