How old is Goku in dragonball gt

He is 50 years old in Dragonball GT.

In Dragonball, he was 12 years old

In Dragonball Z, he started as a 24 year-old father, he fought Raditz and and died for 1 year (Didn't age). He was revived by the Dragonball Z to fight the saiyans (Nappa & Vegeta). In the Cell sagas(5 years later) now 29, he trained in the Hyperbolic Time Chamber and became 1 year older(now back to his normal age) he is now 30. He sacrificed himself and died during the battle against Cell. During the Buu Sagas(7 years later.) Goku was brought back to life by Elder Kai but has not aged at all. At the end of Dragonball Z (10 years later.) Goku is 40 years old. Dragonball Gt takes place 10 years after the end of Dragonball Z