alright i know everything so just stop tryin to guess his age now this is how it goes.
goten is 7 when goten asks gohan if he can go super sayan gohan sais that he was twice gotens age so gohan was about 14 when he transformed he went SSJ2 when fighting cell which wasnt much latter, the sayaman saga is 7 years after the battle with cell so add 7 years to 14 and you have an age of atleast 21 simple maths people just gotta think.