The height of the UITabBar seems to have changed between iOS 7 and 8/9/10/11. I'm posting this question for others to easily find the answer.
So: What's the height of a UITabBar on iOS 8/9/10/11 on iPhone and iPad?
For iOS 8, 9, and 10 the height is 49 points, both on iPad and iPhone and both in portrait and landscape. It used to be 56 points on iOS 7.
For iOS 11, things get a bit more complicated:
In portrait and regular landscape, the height is still 49 points. In compact landscape, the height is now 32 points.
On iPhone X, the height is 83 points in portrait and 53 points in landscape.
iOS 9 and iOS 10 still uses 49 points for the Tab Bar (and 64 points for a navigation bar) Thanks for the self Q/A, was actually helpful to conform what I had on storyboard.
来源：https://stackoverflow.com/questions/25550831/whats-the-height-of-a-uitabbar-on-ios-8-ios-9-ios-10-and-ios-11