The Street Fighter series has a rich lore with a variety of characters of different ages and origins. Unfortunately the series jumps around a lot in time, with some newer games taking place before older ones in the timeline. For example, the events of Street Fighter 6 canonically takes place after Street Fighter 3. Capcom has always been reluctant to share the exact ages of their characters, but we can use the ages of other characters to figure out how old Ryu is in Street Fighter 6.
Ryu’s age in Street Fighter 6
In some specific versions of Street Fighter 2, most of the characters were given birthdays with their birth years included. While Capcom has not revealed their ages for Street Fighter 6 they have confirmed that Ryu was 33 years old during the events of Street Fighter 3. Game Director Takayuki Nakayama tweeted about Ryu from the official Street Fighter Twitter account saying, “Although Street Fighter 6 occurs after the Street Fighter III series, Ryu still feels that he's "not there yet" - though he seems to have gained some dignity. The way he wears the kasaya (Buddhist robe) is reminiscent of his master, Goken."
During the events of Street Fighter 3, Ryu’s friend Ken talks about his 3-year-old son Mel Masters. Mel Masters also makes a recent appearance in the Days of the Eclipse comics released by Capcom.
In Days of the Eclipse, Mel has somewhat grown-up and is now a teenager. Assuming Mel is somewhere between the ages of 13 and 15 in the comics (based on his appearance), it has been over a decade since the events of SF3. Since Ryu was 33 during the events of Street Fighter 3 that puts Ryu’s age somewhere between 43 and 45 years in Street Fighter (SF) 6.
Similarly, Li-Fen, Chun-Li’s adopted sister is between 6 and 8 years old during SF3 and SF5. Li-Fen features in both the Street Fighter 6 trailer and the Days of the Eclipse comics, she is an older teenager, putting her between 15 and 17 years old.
This further cements the assumption about how much time has passed between SF3 and SF6.
The time-skip marks a massive jump for the series with earlier games being more closely placed. This makes sense with Capcom’s fresher take on the game, passing the mantle to newer fighters like Jamie and Lily, a descendant of the Thunderfoot tribe (famous for T. Hawk).
This 6–10 year hypothesis does make sense with what Capcom is seemingly trying to do with the franchise now by introducing a brand "new generation" of fighters beyond the previous bunch that were already given that title.