Katy Perry knows there is an "expiration date" on her outrageous fashion choices.

The 'Firework' singer is renowned for her crazy dress sense - appearing in costumes including a dress shaped like a cake, one styled as a Christmas tree and others adorned with fruits, die and holes, as well as many latex dresses - but accepts she will one day be too old to wear such wild clothes.

She told People.com: "They have an expiration date and that's why I'm wearing them now at 25. I'm such a sucker for a theme, so if I go somewhere like Las Vegas, I'll dress like Vegas! Or if it's Christmas time, I'll dress like Mrs. Claus!

"I've always been girly - even though I was a tomboy. My mother said when I was a kid, I was changing for breakfast, lunch and dinner. I don't make it a big deal, I just do it."

The stunning star - who married British comedian Russell Brand last month - added that while she can't help choosing outrageous outfits, she does reserve most of them for when she's onstage.

She said: "I think sometimes with the themed stuff - I won't be wearing that to get my coffee. Although, maybe my whipped cream bra I'll wear, because I'll help the baristas out. 'I got it! I got it! Hold the cream! No worries.'"