How tall could a T-Rex get?

It's too bad there aren't any T-Rexes around today to enjoy the love and adoration us humans have for them. Yes, I've seen all the Jurassic Park movies, I know they would just kill me if I ever met one, but so far that hasn't happened so I will continue to think they are cool.

T-Rexes also take a lot of heat for their forearms — but you know what? We should actually give them a break. While their arms were indeed small relative to overall body size, as Wikipedia puts it, "the bones show large areas for muscle attachment, indicating considerable strength."

Not only that, while they obviously weren't the tallest dinosaur out there, they definitely would have been intimidating. How tall could a Tyrannosaurus rex get?