Perry, 27, tied the knot with Brand Oct 23 in India. However, the two parted ways after 14 months of their marriage.
"Katy has been dreading October 23 for weeks now and has been trying to think of ways to turn it into something positive," thesun.co.uk quoted a source as saying.
"She has decided to call it her divorce party and it will be a day of doing what she loves with her favourite people," the source added.
On Oct 25, Perry will turn 28.
"It's her birthday two days later and the last thing she wanted to do was spend that week depressed and miserable, which would then mean not doing anything to celebrate her birthday," the source said.
"Her pals have been persuading her to have a huge party or go to Vegas for a few days but Katy decided on throwing a small gathering at her home," the source added.
Perry is currently dating singer John Mayer.
Photos: Abhishek Bachchan and Farah Khan at Boman Irani's birthday bash
Spotted: Shah Rukh Khan at Morani's bungalow in Mumbai
Spotted: Sonam Kapoor and sister Rhea at Mumbai airport
Photos: Ranveer Singh, Vaani Kapoor get 'Befikre' on 'Super Dancer'
In pictures: 12 child artistes who turned into beautiful divas