What is the top bar height of iPhone X?

Nav bar is 44pt as usual (when no large titles) and the status bar has increased from 20pt to 44pt. Here's what you can type in the debugger to verify it:

You can programmatically obtain the navigation bar's height by using safeAreaInsets on the view in the contained view controller:

let navBarHeight = view.safeAreaInsets.top

This will account for whether it's a large title navigation bar or not, and whether or not there's a search bar attached to it.

See the safeAreaInsets documentation for more information.

You can use the navigation bar's .frame property to figure out the overall height of the top bar area:

Swift 5.0:

let xBarHeight = (self.navigationController?.navigationBar.frame.size.height ?? 0.0) + (self.navigationController?.navigationBar.frame.origin.y ?? 0.0)

ObjC:

CGRect navbarFrame = self.navigationController.navigationBar.frame;
float topWidth  = navbarFrame.size.width;
float topHeight = navbarFrame.size.height + navbarFrame.origin.y;

I suppose this is a bit of a cheat, but adding the navbar's height with its y origin seems to give the correct total height regardless of device.

You can simply get it in the next way (Swift 3):

let barHeight = navigationController?.navigationBar.frame.maxY

To get correct value make sure that you call it after setting prefersLargeTitles

navigationController?.navigationBar.prefersLargeTitles = false

If you're using a UIWindow and you need to know the top bar height you can use this:

// old way of getting keyWindow
//guard let keyWindow = UIApplication.shared.keyWindow else { return }

// new way of getting keyWindow
guard let keyWindow = UIApplication.shared.windows.first(where: { $0.isKeyWindow }) else { return }

let navBarHeight = keyWindow.safeAreaInsets.top

print("navBarHeight:" , navBarHeight)

I got the idea from @Paolo's answer

Use it if you want to know where need start content

extension UIViewController {
  var navigationBarbarContentStart: CGFloat {
    return self.navigationBarTopOffset + self.navigationBarHeight
  }
  var navigationBarTopOffset: CGFloat {
    return self.navigationController?.navigationBar.frame.origin.y ?? 0
  }

  var navigationBarHeight: CGFloat {
    return self.navigationController?.navigationBar.frame.height ?? 0
  }
}