For me he is between 16 and 17 years old

I think he's 15-16

Between 16 and 17

12-17 years old

12(debut)

Finn turned 13 in "Mystery Train"

After season 3 ended he was 14

Finn was 15 years old in the second half of season 5

Season 6 final "The Comet" Finn Revals that he has reached 16 years of age

So Finn is currently 16 years old

So to 12-16 😍