It depends on what you want to know. Pure physical lines is one thing, "size" is a another.

I want a way to measure how complicated a program is that's independent of language and obviously extraneous things like line length.

You may find that the Halstead metrics I mentioned are closer to what you're after.

I've changed my mind. I'm interested in what I originally said: what's the best way to measure code size, and what are those studies (if they exist). Otherwise we get into debates about size vs. complexity, which is actually less interesting IMO. Size as a proxy for complexity is good enough for me.