The Doctor's age

Contradictory information has pointed at different estimates of the Doctor's age, both in conversations and in terms of the length of various incarnations.

Statements and known information
It is unknown what the Doctor's life expectancy is, given his ability to regenerate. The Second Doctor once stated that as a Time Lord he could "live forever, barring accidents" though it's unclear whether this is accurate or an exaggeration. (DW: The War Games) It is also evident that Time Lords age in a different way to humans. The Fourth Doctor once said to his companion that he was a teenager for fifty years. (DWM: The Time Witch) He has also gone through spans of linear time longer than average human lifespans without growing visibly older. (EDA: Escape Velocity, BFA: Orbis, DW: The Impossible Astronaut)

First Doctor
The Doctor was eight when he entered the Academy, along with The Master (DW: The Sound of Drums) and ninety when he first visited the Medusa Cascade. He later described himself as having been "just a kid". (DW: The Stolen Earth) He said he was a "teenager" for fifty years. (DWM: The Time Witch) When the Fourth Doctor was seven hundred fifty-nine, (DW: The Ribos Operation) Romana noted the Doctor had been travelling in the TARDIS for five hundred twenty-three years. This would have made the Doctor about two hundred thirty-six when he first 'borrowed' the TARDIS and left Gallifrey. (DW: The Pirate Planet)

This figure was broadly supported by the TARDIS itself. When transferred into a humanoid body, the TARDIS said the Doctor had travelled with it for seven hundred years. At this point, the Doctor was around nine hundred nine years old, putting his age when he stole the TARDIS about two hundred. (DW: The Doctor's Wife) During the time Susan Foreman travelled with the Doctor, Ian Chesterton, and Barbara Wright, she knew that despite his apparent maturity, in terms of their own species the Doctor was considered an adolescent. (CC: Here There Be Monsters) He stated he had been travelling in the TARDIS for sixty years when he visited 64, putting his age at two hundred ninety-six.. (PDA: Byzantium!) The Doctor spent "centuries" studying at the Time Lord Academy. (DWM: Mortal Beloved) Magnus chided the First Doctor for not regenerating and for holding on to this incarnation as long as he did (DWMS: Flashback). This incarnation regenerated when about four-hundred fifty. (DW: The Tomb of the Cybermen)


 * The first non-fictional writing about regeneration, DWAN: "The Phoenix in the TARDIS", stated that the first Doctor was about 900 at the time he was replaced by the second Doctor.

Second Doctor
At some time after his first regeneration (but not long after given the presence of Jamie McCrimmon), the Doctor made the first known direct reference to his age. He told Victoria Waterfield, he was "something like" four-hundred fifty years old. (DW: The Tomb of the Cybermen). The Doctor seemed to have aged visibly by the time he went on a mission for the Time Lords to Space Station Chimera (DW: The Two Doctors).


 * It is unclear when these events actually took place within the era of the Second Doctor. He may have been taken out of time during a point prior to The War Games. See Season 6B for a longstanding theory involving the Second Doctor's activities after the trial.

Third Doctor
This incarnation of the Doctor started to say that he had been a scientist for "several thousand" years, but stopped himself before completing the sentence. (DW: The Mind of Evil) He had said something similar shortly before that incident. (DW: Doctor Who and the Silurians).

Fourth Doctor
The Fourth Doctor seemed to be seven hundred forty-eight at his start. (DW: Planet of the Spiders) He consistently said he was about seven hundred and fifty-seven or seven hundred forty-nine when he travelled with Sarah Jane Smith (DW: The Brain of Morbius, The Seeds of Doom), a year older with Leela (DW: The Robots of Death) and seven hundred fifty-six with Romana during her first incarnation just before finding the first segment of the Key to Time. Romana corrected him, saying he was seven hundred fifty-nine. (DW: The Ribos Operation)Before they assembled the Key to Time, he turned seven hundred sixty. (DW: The Power of Kroll) Another time,he said he was possibly seven hundred thirty, but couldn't remember his actual age. (DWM: The Time Witch) He claimed at various times to be anything from four hundred to a shade over a thousand years old. (MA: Evolution)

Fifth Doctor
The Doctor said he was eight hundred thirteen when he regenerated (MA: Cold Fusion)

Sixth Doctor
The Doctor said he was nine hundred years old (DW: Revelation of the Daleks) and later amended it to "more or less". (DW: The Mysterious Planet) At some point in his past, he had blown out the candles on his nine hundredth birthday cake. (BFA: The One Doctor) At another time, he was nine years shy of an even thousand during his travels with Melanie Bush. (BE: A Wee Deoch an ...?) He was nine hundred fifty-three years old when he regenerated. (DW: Time and the Rani)

Seventh Doctor
Hours after his regeneration, the Doctor unlocked a door in the Rani's laboratory with the numerical code "953," saying it was his age and the Rani's. (DW: Time and the Rani) The Doctor had his thousandth birthday while travelling with Ace and Bernice Summerfield. (NA: Set Piece) He spent millions of years in a coma, frozen in a block of ice; while his clothing had rotted away with the passing millennia, his body was preserved in suspended animation and he recovered fully. (BFA: Frozen Time) By the time of his next regeneration, he had aged visibly. (DW: Doctor Who) By his own estimate afterward he would have been a thousand nine when he regenerated, though he admitted he may have lost count at some point. (EDA: Vampire Science)

Eighth Doctor
Three years after his regeneration, the Doctor calculated his total age to be one thousand twelve. He was unsure and might have lost count. He began at his most recent regeneration, giving his age as "three" when asked. (EDA: Vampire Science) The Doctor aged while trapped as an amnesiac on Earth in "real time" between the late 19th century (EDA: The Ancestor Cell) and the year 2001, making him at least eleven hundred twenty-five by the end of this crisis. (EDA: Escape Velocity) While travelling with Lucie Miller, the Doctor spent six hundred years on the planet Orbis. He later mentioned that he rounded and adjusted his age based on different year lengths in different parts of the universe. (BFA: Orbis)

Ninth Doctor
This incarnation claimed "nine hundred years of time and space", i.e. travel in his TARDIS, and said that this was his age. (DW: Aliens of London) He later claimed to have used the name "The Doctor" for nine centuries and to have had "nine hundred years of phone-box travel" (DW: The Empty Child).


 * See 'The "900" Controversy' below for an out-of-universe discussion of this change.

Tenth Doctor
The Doctor said he was nine hundred three years old (DW: Voyage of the Damned) In a parallel universe, he claimed to have given away ten years of his life to give the TARDIS the energy. (DW: Rise of the Cybermen). The Doctor's claim is questionable. Before to the Titanic incident he is known to have spent at least thirty-three months searching for Martha Jones in deep space (DW: The Infinite Quest), and several months (at least) living in various time periods on Earth (DW: Human Nature and DW: Blink). He again claimed nine hundred three during an adventure with Donna Noble. (NSA: The Nemonite Invasion). In a later adventure in America,he said nine hundred again, suggesting he was rounding down. (DW: Dreamland) Just prior to regenerating, he gave his age as nine hundred six, suggesting that several years had passed for the Doctor after his travels with Donna Noble. (DW: The End of Time)

Eleventh Doctor
When Amy Pond first encountered the Doctor, he told her that he was nine hundred seven (DW: Flesh and Stone) and again when meeting the Dream Lord. (DW: Amy's Choice) When he encountered Amy, Rory and River in Utah, he gave his age as nine hundred nine. (DW: The Impossible Astronaut) The Doctor estimated that he was around George's age "about a thousand years ago". (DW: Night Terrors) When he summoned Amy and Rory to Utah, he told Amy that he was eleven hundred three.(DW: The Impossible Astronaut)

The "900" Controversy
The writers of the 2005 revival of the series explicitly describe the Doctor as nine hundred years old, despite contrary statements on TV and expanded media. It is one of the few notable contradictions to established canon in the revival. Although as noted above it's possible to suggest rationalisations (and fans have suggested others ranging from Time War-related trauma to speculation of an unchronicled adventure in which the Doctor was "de-aged" much as he was "aged" in DW: The Sound of Drums and Last of the Time Lords), to date no episode, novel or comic strip has addressed the discrepancy.

"He Has No Clue"
A simple and self-evident theory is that the Doctor doesn't know how old he is. Constantly travelling backward and forward through time makes it difficult to measure one's lifespan at all. This theory has been fanon, and the Doctor occasionally admitted to being unsure of his age in spinoff media. (DWM: The Time Witch, EDA: Vampire Science) This is the theory subscribed to by Doctor Who's current executive producer and head writer Steven Moffat in an interview with SFX: "The thing I keep banging on about is that he doesn't know what age he is. He's lying. How could he know, unless he's marking it on a wall? He could be 8,000 years old, he could be a million. He has no clue. The calendar will give him no clues."

- Steven Moffat, SFX, May 2010 Moffat reaffirmed this on his Twitter blog.