1. Lady Capulet's Statement: In Act I, Scene III, Lady Capulet, Juliet's mother, mentions that Juliet is "not fourteen years old." This suggests that Juliet is approximately 13 years old at the time.
2. The Nurse's Comments: The Nurse, Juliet's caretaker and confidante, frequently refers to Juliet as a "girl," "young mistress," or "child." These terms imply that Juliet is still quite young.
3. Juliet's Immaturity: Throughout the play, Juliet's behavior and emotional responses display a certain level of immaturity. Her quick infatuation with Romeo, her impulsive decisions, and her intense reactions to events suggest a youthful innocence.
4. Legal Age for Marriage: During Shakespeare's time, the legal age for marriage for women in England was 12 years. Juliet's parents are planning to arrange a marriage between her and Paris, which indicates that she is of marriageable age according to the societal norms of the time.
It's important to note that while the play does not provide an exact age for Juliet, the references and contextual clues strongly suggest that she is a very young teenager, likely between 13 and 14 years old.