Bilbo Baggins was 50 years old when he left the Shire in The Hobbit. Gandalf and the dwarves arrived at Bag End shortly after Bilbo’s fiftieth birthday, drawing him into the quest to reclaim Erebor.
Bilbo’s age matters because hobbits traditionally value routine, comfort, and an untroubled domestic life. At fifty, he is established as a respectable resident of Hobbiton, yet his Took ancestry gives him a suppressed appetite for adventure. The quest forces those contrasting sides of his character into conflict.
The number is often confused with Bilbo’s later birthday age. In The Lord of the Rings, Bilbo celebrates his 111th birthday at the famous party held in Hobbiton. He also leaves the Shire on that occasion, but that is a later event, not the beginning of his journey in The Hobbit.
Bilbo’s adventure lasts roughly a year before he returns home. His experiences change his reputation and his understanding of the wider world, while the discovery of the Ring connects his story directly to the later history of Middle-earth.