How to get height of topLayoutGuide?

You can get the topLayoutGuide value as its length property:

// Inside your viewController
self.topLayoutGuide.length

Since it is a single value (i.e.: it does not have a height and width) they just called it length. Same holds for bottomLayoutGuide.

Hope this helps

One more thing to mention, in the apple doc for this property:

// As a courtesy when not using auto layout, this value is safe to refer to in -viewDidLayoutSubviews, or in -layoutSubviews after calling super

Use this property in these two functions will get you the accurate value, since the layout has been initialized. If you use it in the viewDidLoad function, this property will be 0.

If someone is looking for how to calculate the height of insets of SafeLayoutGuide available for iOS 11 because Top and Bottom Layout Guide are deprecated now, you can find it in:

view.safeAreaInsets

Notice that Top and Bottom Layout Guide were a part of ViewController, and now SafeLayoutGuide is a part of the main view of the ViewController.