Sienna Miller is looking forward to a "more serious decade" when she turns 30.

The actress will reach the milestone age in December and can't wait to leave her 20s behind her after a series of unsuccessful love affairs, including relationships with Jude Law and the married Balthazar Getty, and faux pas such as remarking that people take drugs because they're "f**kloads of fun".

She said: "I think, if you put a camera in anyone's life and document it daily from the age of 21 to 27, there are going to be things that aren't always pretty. I feel as though I experienced my 20s in all their glory and all their disastrousness. Now, I'm much more calm. It feels like a new, more serious decade.

"Things just come out. I'll say the most inappropriate things at the most inappropriate time to the most inappropriate person. Always. I can't wait to be seen as a woman. But I know I probably have to contribute to that with behaviour."

However, Sienna admitted working in youth obsessed Los Angeles has led her to have some reservations about growing older.

She added to Australia's Herald Sun newspaper: "Recently, I found myself thinking, I'm getting wrinkles. And things are wobbling, I should go to the gym. Then I was like, f**k it. That's not where the focus should be. Los Angeles is a nightmare for that. I say, people should be young and then be old."