The singer revealed the unglamorous side of touring, explaining that although she looks like pristine when she walks out on stage, the backstage reality is very different.
"You walk on stage feeling like Mary Poppins but really you've just had your skin zipped, peed in a bucket and been dry-heaving over the trash can," she is quoted by The Sun as saying.
Perry recently insisted that she will quit music when she doesn't enjoy her job anymore, confessing: "I can't be the candy queen forever."
The star's documentary film Part of Me 3D is in cinemas now and follows Perry on her gruelling 'California Dreams' world tour.
Watch Digital Spy's interview with Katy Perry at her film's UK premiere below: