20 Daniel Radcliffe (11) - Harry Potter (11)

Debuted In Harry Potter And The Sorcerer's Stone

Beginning with the first film in the series, Harry Potter and the Sorcerer's Stone's differences to the book were minimal. This extended to the age of the titular character in comparison to actor Daniel Radcliffe - who, like most of the other child actors in the franchise, were specifically chosen to align in age to their book counterparts.

When filming began in 2000, Daniel Radcliffe was 11 years old. His character, Harry Potter, has his 11th birthday in the film's first act, meaning the accuracy was almost dead on regarding the ages of Radcliffe and the Boy Who Lived. Having that age explicitly stated in the beginning of the movie is significant as it marks the beginning of his life as a wizard and being exposed to this magical world around him.

19 Rupert Grint (12) - Ron Weasley (11)

Debuted In Harry Potter And The Sorcerer's Stone

Harry Potter and the Sorcerer's Stone also introduced Rupert Grint as Ron Weasley, Harry's best friend at Hogwarts. Ron is presented as the mischievous one in the Golden Trio, with him growing in maturity over the course of the movies but still being a bit goofier than his friends. The fact that he is a younger brother with brighter, more talented siblings also gives him a chip on his shoulder.

Grint is slightly older than Radcliffe, with the actor turning 12 a month before filming began in September 2000. Ron is the same age as Harry in the books and films due to being in the same school year, meaning Grint was one year older than Ron's age of 11 when filming Harry Potter and the Sorcerer's Stone, a barely noticeable difference from the character.

18 Emma Watson (10) - Hermione Granger (11)

Debuted In Harry Potter And The Sorcerer's Stone

The youngest of the three main actors in Harry Potter and the Sorcerer's Stone was Emma Watson. Watson was only 10 years old when filming began on the first film, making her slightly younger than her costars. Just like Harry and Ron, Watson's Hermione Granger was 11 in Harry Potter and the Sorcerer's Stone, meaning the actress was slightly younger than her character counterpart.

This presented an interesting challenge for Watson when taking on the role, as Hermione is always a character who is seen to be wise beyond her years. She is not only a brilliant and dedicated student, usually showing up her fellow Hogwarts classmates, but she also acts as the most rational member of the group of young heroes. She comes up with plans, steers her friends away from poor decisions, and keeps them out of trouble as much as possible.

17 Tom Felton (13) - Draco Malfoy (11)

Debuted In Harry Potter And The Sorcerer's Stone

Another of Harry, Ron, and Hermione's fellow pupils in Harry Potter and Sorcerer's Stone is Draco Malfoy, Harry's Slytherin bully. Also supposed to be 11 in the film, Malfoy actor Tom Felton holds the biggest age disparity between actor and major Hogwarts character. Felton was born in September 1987, meaning he turned 13 during the first month of filming on the series.

The older age of the actor actually helps to define Felton's performance in the movies. Draco is shown to be cockier than his fellow first-year students, especially Harry Potter. Having Felton be older than them adds to this dynamic even if the characters are meant to be the same age. Of course, Draco can often seem like one of the most immature characters with his tough and confident attitude often shrinking away at the first sign of danger, right up until Draco's ultimate redemption.

16 Matthew Lewis (11) - Neville Longbottom (11)

Debuted In Harry Potter And The Sorcerer's Stone

Alongside Harry, Ron, and Hermione in Gryffindor house was Neville Longbottom, with his debut also coming in Harry Potter and the Sorcerer's Stone. And like his peers, Neville's age was also 11. Neville was definitely one of the shyer students at Hogwarts, and unsure of himself in these early days, and as a result, Neville felt a lot younger than the rest.

Actor Matthew Lewis had turned 11 three months before filming began on the first film. He fits nicely into the timid youngster role that made the meek Neville such a fan-favorite Harry Potter character. However, those early days of Neville at Hogwarts only made his eventual arc all the more satisfying as he gradually found more confidence in himself and even took on more of a leadership role among the heroic Hogwarts students.

15 Harry Melling (11) - Dudley Dursley (11)

Debuted In Harry Potter And The Sorcerer's Stone

While not playing a major role in the first film, Harry's spoiled cousin, Dudley Dursley, was also introduced in Harry Potter and the Sorcerer's Stone. In many ways, Dudley is the first villain Harry faces in the movie as he mistreats his cousin and makes his life as an orphan even more miserable. In both the first book and film, Dudley's birthday is shown as being around a month before Harry's. The two are therefore essentially the same age, with Dudley being 11 throughout the first film.

Harry Melling, the actor responsible for playing Dudley, was also 11 when filming for Sorcerer's Stone began. Having Harry and Dudley the same age is an effective way of showing how differently the two children live. While Harry makes the best of his lonely and put-upon life, Dudley is given everything he could possibly want and still finds a lot to complain about.

14 Bonnie Wright (9) - Ginny Weasley (10)

Debuted In Harry Potter And The Sorcerer's Stone

Another character whose role grew as the series went on yet debuted in Harry Potter and the Sorcerer's Stone was Ginny Weasley, Ron's younger sister. Ginny is a year younger than Ron in the first film as she starts Hogwarts in Harry Potter and the Chamber of Secrets, meaning she is 10 years old when Harry first meets her. She is not much of a prominent character in the first movie but becomes more important in the sequel.

Bonnie Wright played Ginny throughout the Harry Potter film series and was one of the youngest core cast at only nine years old at the time of filming beginning. It has often been discussed why J. K. Rowling decided to include a romance between Harry and Ginny, given she was the little sister of Harry's best friend. However, the age difference between the characters is not very noticeable nor is it substantial.

13 Evanna Lynch (15) - Luna Lovegood (15)

Debuted In Harry Potter And The Order Of The Phoenix

Luna Lovegood is a character whose first appearance came in Harry Potter and the Order of the Phoenix, yet she played an integral role in the final four movies of the series. Lovegood is a Ravenclaw at Hogwarts and was 15 years old at the time of her debut as Harry meets her during his fifth year at the School of Witchcraft and Wizardry.

Evanna Lynch, Lovegood's actress, was also 15 when filming began for Harry Potter and the Order of the Phoenix. Luna's age in the story is an interesting detail as she is another character who seems wiser than her years, seeing things that others don't and providing useful advice to Harry and the others. However, she also has a spacey quality to her that makes it seem a little like she is an even younger child wandering through this magical world.

12 Gary Oldman (44) - Sirius Black (34)

Debuted In Harry Potter And The Prisoner Of Azkaban

Sirius Black's role in the third through fifth Harry Potter movies cannot be understated as an important member of Harry's family. While the films do not specifically divulge Black's age, the books state he was born in 1959, meaning he was 34 in Harry Potter and the Prisoner of Azkaban. Despite the film series being a more modern retelling of the books, it can be assumed the timeline is similar and Black was 34 in his film debut.

Oscar-winner Gary Oldman portrayed Sirius Black and was 44 when filming began on the third film. It is not surprising that the movie was willing to stretch the age of the character somewhat to get an actor of Oldman's caliber on board. Also, with Daniel Radcliffe being 15 by the time Prisoner of Azkaban came about, having an older character with appropriate gravitas step into this paternal-like role was essential.

11 Ralph Fiennes (41) - Voldemort (68)

Debuted In Harry Potter And The Goblet Of Fire

Despite appearances in various forms in earlier films, the series' main villain, Voldemort, was properly resurrected in Harry Potter and the Goblet of Fire. Voldemort's age is up for debate, given his various life forms throughout the series. However, the time between Tom Riddle's birth and Voldemort's resurgence in Goblet of Fire was 68 years.

Though several actors played Voldemort at various stages of his life throughout the franchise, Ralph Fiennes became the iconic version of the villain, bringing him to life between Goblet of Fire and The Deathly Hallows: Part 2. Fiennes was 41 when filming began on the former film. While there is a big discrepancy between the ages of the character and actor, it is not something that is noticeable as Fiennes dons extensive makeup that not only makes Voldemort less human but also succeeds in making him appear older. In addition, wizards live longer than muggles in this world, so older wizards often appear younger than they otherwise would.