How old do you have to be to sit without a booster seat in the car?

I would say you have to be at least 8 years old but then again it depends how tall you are. i your over 8 and you can't see out the window then you might still need the booster seat which is fine however, if your under 8 but your way taller and you can see out the window then i don't see why you can't get rid of your booster seat.