How do I find the physical length of a string?

[appadmisy]

In my website, the user's username is always displayed at the top of every page (along with the site title, other page links, etc.) in a font size of "3"It took me a really long time to figure this out, but it eventually came to my attention that the users with really long usernames ended up messing with the spacing at the top of every page and all the text gets pushed down a line, making the whole thing look ugly as sin (it's only visible to the individual user since it's their username, but I don't want any of my users seeing it at all).I'm not asking how to find the number of characters in their name -- what I want to know is how I can determine the physical amount of space their name will take up and, in the event it will be too long, reduce the font size to 2, or even 1 if necessary.The reason why a simple strlen() wouldn't work is because of the potential space differences ("Tragic Dionysus" takes up less room than "HERSHEYFEVER", regardless that the former has more characters in it).An extensive Google search continually leaves me with more character counting methods, so I'm left clueless.