Is there a way to measure the pixel with/height of a string with a given font?

I see the GUI Layout stuff for automatically laying out UIs in certain ways. And that is pretty cool overall. However, it is also really helpful to be able to precisely center various arbitrary strings (arbitrary thanks to localization or other factors, which has been an interesting challenge for me in past projects). With both DirectX and GDI, there is essentially a MeasureString method that you can pass a font, some text, and a max width to, and it gives back a Size property saying how wide/tall that text will be given the parameters you passed in. Surely there's something similar in Unity?

You can use GUIStyle.CalcSize() which takes a GUIContent as parameter:

Vector2 sizeOfLabel = myStyle.CalcSize(new GUIContent("My string"));

You can use this on a GUIStyle you have made that uses the font of your choice.

GUILayoutUtility.GetRect() reserves space for the rect it returns, so it may influence your GUI layout. If you want a function that does not have side effects, CalcSize is the way to go.

Yes, you can use GUIUtility.GetRect(), where you pass in GUIContent and GUIStyle and get back a Rect. (Plus various overloads.)