We know from Madara himself in manga chapter 398, that Konoha was founded over 80 years before part 2, which would basically be 80 years before the Uchiha Clan Assination. We also know from j-man that madara would have to be over 100 years old, so... Since young madara was the Uchiha leader at the time of Konohas founding, we can assume that he was between 30 and 40 (based on the average age of a clan leader before having children, like Hiashi who was that age before having Hinata), so we'll say 35; then add that age back too the original 80 years before Uchiha assaination, we'll get 115. THEN... if we add the 8 years between Uchiha assaination and now in part 2 (since sasuke was 8 during the tragedy and is almost 16 now) to the 115, we'll end up with a very good guess of Madara being around 123 years old now. Whew! that was alot of math lol