If you go by Gandalf's age as a Maia in general, he'd be as old as the world. So, roughly 10,000 years, if you don't account for the fact that the Years of the Lamps and the Years of the Trees were longer than a standard year.

If you go by when he showed up in Middle-Earth as Gandalf the Grey in year 1000 of the Third Age he'd be 2018 at the time he confirms Bilbo's ring is the One and confronts Frodo about it in year 3018 of the Third Age.

Gandalf The Grey would have been 2019 years old when he was mutually slain by Durin's Bane after falling from the bridge in Khazad-Dum.

Gandalf The White then first appeared a few months later and would be only two years old at the time he sails west with Frodo, Bilbo, Galadriel, and Elrond.

[–] Crackhappy@lemmy.world 1 points 3 months ago (1 children)

A couple decades ago, I actually tried to calculate it and came up with somewhere close to 13,000 years, adjusting for the wonky time. There are also somewhat contradictory numbers too (such as when Gandalf says how long he's been alive).

[–] i_love_FFT@lemmy.ml 2 points 3 months ago

Being older than 30, I can understand that a being older than 1000 would get confused about their age (especially if the time unit changed since they started counting!)