What is the definitive iPhone X corner radius?
iPhone X corners do not have a conclusive corner radius. They're not normal arcs, they are ‘continuous corners’.
You can't replicate these with a simple .cornerRadius, and you also can't use Apple's own continuous corners, since that's a private API.

CALayer on iOS 11 has a private &quot;continuousCorners&quot; property, which is what powers many rounded corners in SpringBoard – and likely more! Now I'm jealous.


https://twitter.com/argentumko/status/955773459463790592
The closest you can get without your own implementation is UIBezierPath's rounded rectangle drawing, which uses _continuousRoundedRectBezierPath.