The Doctor’s age is allegedly something like 900 or so years. Given his recent track record, either he’s got some early or entirely off-screen cycles, or he’s been cheating on his regenerations.
So are there canon estimates of his time in each version?
He burned through regenerations pretty quickly before Eight and the official Nine. He’s probably up to Thirteen or Fourteen.
There is plenty of space between seasons, and even between episodes, that extend his life beyond what we see in the show. He could easily have a human length lifetime each regeneration.
Going by the official tally, Tennant was #10, making the new guy #11.
The question is, how does one determine the age of a time traveling alien? Would YOU have any clue how old you are if you travelled through time or space? Time or space, not even time AND space.
The fact that they are jumping around in time doesn’t mean that time doesn’t pass. I would expect a Time Lord to be able to track time as it passes - something like TARDIS Local Time.
Presumably the TARDIS is with him in all of his adventures and, therefore sharing his point of reference, can serve as an accurate chronometer (with occasional adjustments when he temporarily misplaces it).
Also, he’s with humans most of the time now. Humans need sleep at regular intervals in a way that is linked to a 24 hour ish day. It wouldn’t surprise me, based on his proclivities, if the TARDIS wasn’t set on GMT 
The Doctor obviously has had a LOT of adventures we never saw. If this article on the Doctor Who wiki is accurate, less for each subsequent Regeneration.
His second Regeneration once said he was around 450 years old.
Four said 750.
He’s claimed 900 and change since Six. Except for claiming to be over 1000 as 8. (Though I do like the theory that he’s stopped counting his first couple hundred years since then - with Galifrey gone away, due to his own actions, and, well, the people there having gone pretty much over the edge, the last he saw them…)
So, the first four incarnations lasted…let’s call it 800 years. The first 400 are on the first, so that’s an average of ~133 years per for 2-4.
The next 6 lasted…let’s assume he’s taken to ignoring his life pre-Tardis, and say he’s about 1200 now, so that makes 400, giving us an average of 67 years per. Given 9’s short tenure, most of which was spent with Rose, so can’t be too much longer than than what we saw, we can probably up 5, 6, 7, 8, and 10 (who spent quite a bit of time companionless, and explicitly claims a lot of adventures during those times) to 75 or so. Or keep 10 at around 60, and up the others to 80 or 90.
Like the ages of the actors, then, his time between regenerations has been trending downwards, with occasional spikes. Since they’ve generally gotten more reckless as time’s worn on - and in 9’s case, arguably suicidal - with, again, occasional exceptions, this makes sense.
Oh, duh, I completely brainfarted on the fact that 5 is, necessarily, ~100 years or so. Which only slightly nudges the numbers, of course.
But, let’s redo the math a bit, anyway.
The last 5 lasted 300 years, meaning an average of 60 years. Let’s call that accurate for 10, and assume 9 was only a year or two (because, again, Rose’s lack of aging reduces the number of off-screen adventures he could have).
Meaning 6, 7, and 8 had 238 years between them. That gives us an average of about 80 years.
So, assuming my estimates are about right, and then going with the averages, we’ve got…
400
133
133
133
100
80
80
80
2
60
Which only gives us 1102 years for his total age, not my estimate of 1200. But that’s because of the severe rounding, and may be closer to his actual age, anyway. >_> The averages can be fiddled to estimated ‘real’ times to make the down-trend a little clearer, but…
I got the impression that Doctor Nine was around for a long time before he met Rose. Not having seen anything other than Doctor Eight before NuWho, I guess I just took it from the start that this was a very old character with lots of backstory I didn’t know about.
Was it explicitly stated that Doctor Nine spent most of his time with Rose, or just the last two years or so of his life?
He had to have regenerated very shortly before he met Rose. When he’s rummaging through her kitchen, he catches sight of himself in the mirror. He’s never seen himself before. “Oh, could’ve been worse,” he says. “Look at the ears!”
Well he did have lots of back story, he may just not have been him when he had it!
The first episode contains some conflicting clues. The Doctor seems genuinely surprised when he catches sight of himself in a mirror, as if he hadn’t known what he looked like. On the other hand, the guy with the Web site dedicated to him had pictures of the Ninth Doctor in different decades.
It’s a fairly common belief among obsessive Doctor Who fans that the Eighth Doctor regenerated into the Ninth during or immediately following the Time War. This is bolstered by The Tenth Doctor’s comment to Rose that Doctor 10.5 (if you don’t know, don’t ask) was full of rage, born in battle, just like he was when Rose met him.
As far as the First Doctor’s living so long compared to subsequent incarnations, it can be explained away that the Doctor as originally portrayed was much less likely to put himself in harm’s way for the sake of another.
It’s implied that he regenerated after the Time War that wiped out the Time Lords (sort of) and Daleks (sort of) and destroyed two planets, one being his homeworld. There is a chance he was shellshocked from these events and drifting in time and space for years, decades or centuries before he noticed that he regenerated in Rose’s mirror. The Ninth Doctor did act quite differently from his other personae. Also, the Master had his memories replaced, but once he regained them he started going insane.
Not sure that’s true, I’m sure the 4th Doctor claimed to be over 700 years old in Pyramids of Mars.
I also think the first Doctor claimed to be between 400 and 600, but can’t remember where that was stated.
The tv series has also got out of step with the novels (or vice versa), as the 7th Doctor celebrated his 1000th birthday in one book, but that is obviously not canon.
Also, he spent the first 200 and change (longer than the entire LIFETIME of any other Regeneration - longer than any 2 post-4 Regenerations put together) on relatively peril-free Galifrey rather than gallivanting around timespace in a TARDIS which frequently seems determined to drop him into the middle of the most dangerous situations in history.
Except in series one (2005) he claims to have had “900 years of phone-box travel,” and claims in series four to have visited the Medusa Cascade as a child of 90.
I see above that you assume he doesn’t count his life pre-Tardis, but that seems an unnecessary and illogical assumption. (Yeah, I know, but why introduce *more *illogic into it?
can you cut him open and count the rings?
It seems kind of odd that the Doctor is 900 years old, but all of his regenerations seem to be within the last 50 or so years. But then again, it just seems like that to us. He’s been traveling all around time between those years we’ve seen him on the TV.
To complicate things, in one of the Sylvester McCoy Big Finish audio adventures, he spends 200 years trapped on a planet without his TARDIS.
Audio adventures, novels, animated episodes, short stories, and comic books are best thought of as occurring in alternate universes. It’s the only way of maintaining even the most faintly plausible thread of continuity, and it avoids having to deal with some rather embarrassing concepts that have been introduced over the years. (Genetic looms?)
Actually, it might help to consider each episode, two-parter, or serial as occurring in its own universe.
ETA: I’m reminded of the recent episode in which a gigantic robot devastates large swathes of 19th-century London at Christmas. The Doctor’s companion du jour says something to the effect of “History will long remember the events of this day,” in response to which the Doctor mumbles something like, “Yeah, odd that.”
Official information from the BBC webpage.
In David Tennant’s last story he said he was 903 years old, which contradicts the information in the above link. Maybe he was talking about that particular incarnation.