Ezra is born in 19 BBY. The first season of Rebels occurs in 5 BBY, making him about 14. Each season then adds approximately one year to the timeline until the final season (Season 4) takes place in 0 BBY - that is, not long before the destruction of the Death Star and the beginning of the end for the Empire. Thus, he's about 19 when he commands the purrgil to pull Thrawn and his fleet into the Unknown Regions.