How tall is Sir Vim?

The question should read "was" instead of "is" because Sir Vim and others of the White Knights trees are no longer alive. Severe weather starting in 2013 caused them to die.

Depending on source, the height is given either as 91.3 meters or 89 meters, with the latter being the more recent measurement (2019) and probably reflecting that the tree had already greatly suffered if not outright died at that time.

https://www.wondermondo.com/white-knight-the-tallest-manna-gum/
https://www.monumentaltrees.com/en/records/aus/tasmania/