Board Thread:Questions and answers/@comment-30069821-20161031231921/@comment-8695373-20161102140006

Ages of most characters were not officially revealed.
 * Playable characters
 * We know that Noel is chronologically 5 years old, because she was made on December 25, 2194.
 * Nu is literally 0 years old, since her smelting ended at the end of Calamity Trigger, and the story ended approximately 3 months after that. But, if you count her lives in previous bodies, then chronologically she is around 2 years old, since Ragna went on a Murakumo-killing spree in 2198.
 * Kokonoe is around 90 years old, since she had to be born in 2108-2110, because Nine didn't have any children in Phase Shift 2 (2107) and Terumi disposed of her in 2110.
 * Lambda was alive before Noel's smelting in 2194 (and she also died before Noel's smelting in 2194).
 * Naoto is 16 years old in Bloodedge Experience, but it is unknown how much time had passed for him until CF, so his age in CF is unknown.
 * Es is chronologically 5 years old, according to information we got from both XBlazes, but since it is unknown how much time had passed between LM and CF for her, her age in CF is unknown.
 * Non-playable characters
 * Totokaka is around 90 years old, since she comes from the first generation of Kakas, which was created during the First Magic War.
 * Kazuma is chronologically 8 years old during Phase Shift 1 (because of how much he can remember) and he is 12 at the end of the First Magic War (and that means he was created in 2098)
 * Bloodedge Experience
 * Raquel is chronologically 2 years old
 * Terumi Saya is 13
 * Hayami Haruka and Fukuda Shinnosuke are 16
 * And most of the XBlaze characters have their ages listed in their profiles.

I also remember I saw someone trying to deduce how old are the Military Academy students (Mai and the rest), since the Military Academy is treated like a modern Japanese high school. I can't find that post anywhere, and it seems unlikely that that was viable, since Japanese highschoolers study for 3 years, while we see Jin enter the Academy in 2193 and graduate in 2197, which is four years.