How old was Dean when John died?

26 또는 27. Dean was born in the 년 1979, John died in the first episode of Season 2, so, yeah, Dean was about 27.

He was 27 when John died. In the Pilot Dean says that he's currently 26, and since each season is a 년 long he would have turned 27 의해 season 2 episode 1.