How old do you have to be to choose what parent you live with

18.

Yep 18, before that you can testify in court to the judge to who you want to live with. If you are living with lets say your mom and you want to live with your dad, your dad will have to file with the court for custody and then you can testify, the judge does not have to do what you want, they base their choice on all sorts of things.