What is Spanish for you're so beautiful?

"You're so beautiful" in Spanish is "Eres tan bella". It is pronounced "AIR-ace tahn BAY-ya". Please see this site for confirmation of the translation: http://www.answers.com/library/Translations

It would be better to say, "Qué guapa eres." (Literally, "How beautiful you are!") "Tan" is generally used as a comparison.