'Applause' is also showing promise of a good start with an expected number of 200,000 to 225,000 downloads, according to Billboard.
"Roar" and "Applause" were released to digital retailers on August 12 and 13 respectively.
Perry's 'Roar' is from her album "Prism" which releases on October 22 whereas 'Applause' is the first single from Gaga's "ArtPop", arriving on November 11.
Gaga has been spotted promoting the single by sporting face paint. Gaga's last studio album was 2011's "Born This Way,", which debuted at No 1 on the Digital Songs chart with 448,000 downloads after only three days on sale, according to Nielsen SoundScan.