GUI font size relative to screen size

Alright, so I am working on android, meaning I have to make everything adjust to very different screen sizes. (tablet vs phone). I know how to do the buttons, boxes, etc… However, no matter what I try, I can never get the font sizes of the GUI to change dependeing on the screen size. For instance.

Tablet:
|------------------|
| Load Game | = Big button, big centered text. Works
|___________|


Phone:
|--------|
| Loa…| = Small button, text is still big though, thus it is not centered and is cut off.
|_____|

So, How do I make the font size smaller depending on screen size, so that it will stay centered and the same size relative to the button/box?

Ok, so this makes all my buttons and texts change size depending on the screen size… And the font is tiny, even on a big screen, which makes it impossible to read. I don’t really want to change all my GUI in the whole game, I just want to make the font change size…

Ok, nevermind, found a solution. Thanks for the help though.