How old was Carl Grimes supposed to be during his final episode in The Walking Dead? As the son of The Walking Dead's heroic protagonist, Andrew Lincoln's Rick, Carl was a central figure in the AMC zombie apocalypse series from the very first bite. Growing up in a world of death and fear, Carl's evolution as a character has arguably been the most compelling arc in the entire show - does Rick try and maintain his son's innocence or accept that the luxury of childhood is gone? Does Carl become numb to the pain and gore, or can he be a voice of reason among the warring adults?
Such is Carl's importance to The Walking Dead, Robert Kirkman's original comic series tells its final chapter entirely through Carl's eyes, but the TV adaptation took a different path, controversially killing off Chandler Riggs' character in season 8. The reasoning behind Carl's death will always be somewhat muddled, and another ambiguous aspect to the character is his age throughout The Walking Dead. As many films and TV shows with young characters have discovered, teenage actors often mature a lot faster than their on-screen counterparts, and this can cause havoc with the in-universe timeline. This proved problematic for The Walking Dead, where seasons would air a year apart, but the story might only advance by a few weeks.
While this discrepancy doesn't notice with the adult characters, it certainly did with the rapidly-growing Carl, who goes through puberty before the audience's very eyes in The Walking Dead. When Carl makes his debut in season 1's "Days Gone Bye," the youngster is a tender 12 years-old. Roughly a year passes between then and season 3 when Rick's group are camped out in the prison, making Carl 13 at this point. With a few small time-skips here and there, Carl is most likely 14 during the events of The Walking Dead season 4. Up until this point, Carl's age is relatively straightforward to follow.
The problems occur between The Walking Dead seasons 5 and 8, as the Alexandria and Savior material all takes place within a relatively condensed time frame of only a few months. Chandler Riggs, on the other hand, stubbornly refused to stop growing up. There are no multi-year time jumps during this era and one season finale bleeds directly into next season's premiere. So narrow is the time frame in Carl's final days, there are 3 episodes between the character being bitten and actually dying. When Carl does finally bid farewell in The Walking Dead season 8's "Honor," he's probably 15 years-old, even though Riggs himself was in his late teens. There's a mini time-skip of ambiguous length in the middle of The Walking Dead's sixth season which could potentially push Carl towards 16 in his final episode.
Trying to definitively nail down Carl's age in The Walking Dead is almost as futile as trying to reason with a zombie horde. There is a clear disconnect in Carl's rapid aging that Chandler Riggs himself has acknowledged since leaving the show. Moreover, The Walking Dead's own comic editor previously revealed that Carl's age was something he often disagreed with Kirkman over, and that's without the added trouble of a teenage actor going through puberty. If those devising The Walking Dead can't settle on Carl's true age in the story, there's little hope for fans. As far as the TV adaptation goes, however, 15/16 years-old feels like the best guess when Carl dies in The Walking Dead.
The Walking Dead season 10 is currently on hiatus.