How old is the Doctor at the end of The Time of The Doctor?

We don't know.

If he was 1200 years old at the start, he must have been 1500 years old halfway through the movie, when he looked middle aged. That's when he said he'd been there 300 years.

However, at the end, after another journey in the Tardis for Clara, he looked much older again, so that must have been a considerable time later. And unless I missed it, it wasn't said how long.

My guess is probably another 300 years, because that's how Moffat's mind works. (It was clearly a reference to The Curse Of Fatal Death, where every time he meets The Master, The Master is another 300 years older.) So that would make him 1800 years old.

first time here. I have roughly estimated 1700 years old. he was sulking for one hundred years after Amy and Rory died in Angels Take Manhattan, pre-The Snowmen. then he was 1000 years-old when he met Clara - "I'm an alien from outer space, I'm a thousand years old, I've got two hearts and I can't fly a plane!". I don't remember how long he stayed at the Monastery before The Bells of St. John, but based on that quote it must not have been long, because the monks knew him as a normal person, not someone with a long age length, maybe just the time to grow a beard. then 300 years post sending Clara back in The Time of The Doctor = 1400, then more than 300 years to get to that extent of ageing - after all he did not age that much in 300 years - I did not like the transition makeup. but then again he aged pretty much nothing in 100 years, so it could have been much more after those first 300.

No one's completely sure, but the Doctor is probably around 2000 or 2100 years old now as he apparently stayed on Trenzalore for 900 years.

I actually calculated a rough estimate of his age just after the latest episode aired based on the fact that at one point, the eighth doctor calculated his age at 1012 and must have been a bit older at the time of his regeneration given his physical appearance in the night of the doctor.
Anyhow, I calculated through to Matt Smith's exit and he is no younger than 2000 years old (I dont want to recalculate it all but it is around 2,400. But I could be wrong, so that's why I say no younger than 2000)

In the trailer for the new season, the latest incarnation of The Doctor claims to have

"lived for over 2000 years"

Matt Smith admits that he is 900 (something-ish) during the episode where River actually kills him. The OTHER Doctor that Smith plays at the beginning is 1100 years old - HOWEVER, if I recall right, by the time all is said and done, we get Smith's doctor back at around 900-ish years old, making the new Doctor just under 1,000 by the time he takes over with Clara Oswald. So, HOW can he be "..over 2,000 years old." I"m so confused LOL

The Doctor is roughly between the ages of 1800 and 2500. My guess is that he is 2409 years of age.

If the eighth Doctor was 1012, then the Time War lasted for 400 years, he would have been at least 1412 by his "ninth" incarnation. We don't know how long the "tenth" Doctor was around, as there were off-screen adventures, but the "eleventh" Doctor had at least two hundred years of adventures before spending 900 years on Trenzalore. That would make him at least 2512 by the time Doctor number twelve came around. And that is still assuming he was being honest about his age at all times.

All of yalls logic is flawed. In Matt smith debut season he stated his age as being 900 AND 2000. He said 2000 at the end of The Big Bang. He travelled with Amy the entire time and there was no time passage in the void after the Big Bang. How did he age 1100 years in one season and how is he not 3000 by the end of trenzalore?

Millions or even billions of years old.

In the recent episode The Timeless Children, we learned that

The Doctor didn't know this because his/her memories had been wiped countless times.