The Swiss superstar is tantalisingly close to the impressive milestone.
However, ahead of the ATP Finals in London, he claimed to be relaxed about his chances.
“The 100 happens when it does,” said Federer.
“I hope it happens sooner rather than later, but I’m happy to wait as well.
“I think if I won here it would be more about winning the World Tour Finals and not about winning my 100th.”
The London gathering up is missing one pin-up boy.
British tennis superstar Andy Murray is still out of action after an injury ravaged 12 months.
Murray has been ravaged by injuries over the last 12 months.
He missed the first three Majors of this year due to injury.
The 31-year-old was dumped out of the US Open in the second round.
Murray – who has won Wimbledon twice – then decided to end his season early.
Federer, however, insists the experienced ace can get back to firing on all cylinders.
“I feel you can very quickly play top-30 level,” Federer replied when quizzed about Federer’s return.
“That level he found quickly and very easily, he wasn’t 100% so that makes me feel good about his chances.
“The problem is that he has been No. 1, has won double Olympic gold, it’s not enough to play last-16 or quarters.
“He wants to make top-10 and then top-5, obviously.
“Will he be able to play week in week out or will he have to play less tournaments like I do but still be successful?
“It’s going to be interesting to see how he comes back but I’m confident it’s not going to be a problem if he returns at 100%.”
Federer isn’t quite on top form after losing to Novak Djokovic in the Paris Masters.
He must now battle Kevin Anderson, Dominic Thiem and Kei Nishikori at the ATP Finals next week.