How tall can the funnel of a tornado get?

The funnel of a tornado always connects to cloud base and typically all the way to the ground (the circulation of a tornado can reach the ground even if the funnel does not). Cloud base height is variable but in a tornado supercell is usually about 3000 feet to a mile above the ground. The circulation of the tornado usually goes a great distance above cloud base and can reach heights of more than 4 miles.