I say that Madara had been around 45 during his fight with Hashirama, Tobirama died ~5 years later (according to my calculations) and Naruto was born ~38 years after Tobirama's death. So I'd say that Naruto was born a year after Madara's 2nd death (old age), at about 88 years old. Naruto is now 33 years old (16 years after the great war during which he turned 17 years old). 88+33 = 121 years old, that's how old Madara would be.
Naruto and Sasuke are ~33 years old
And Onoki is 95! (not 100+ how they claimed in anime, because during part 2 he had been 79...79+16 = 95)
This makes Kakashi, Mei and gai ~ 47 years old....
I was kinda hoping for Kakashi and Mei romance...or at least Kakashi and Maki...And Guy + Mei...that would be a superb combo lol