The the Council on Tall Buildings and Urban Habitat is the authority on what building is the tallest. The New Freedom Tower, despite its advertising of being the world's tallest, may not actually be considered such. The occupied space stops at 1,150 ft., the building superstructure itself at 1,500 ft, and the spire at 1,776 ft. "In other words, about one-third of the Freedom Tower will be more of a structural framework than a habitable building." John Lumea of the Phoenix Project, said, "The world's tallest building moniker is a shibboleth of feel-good boosterism perpetrated by rebuilding officials who have nothing else to offer the public but a P.R. campaign."
Thanks to Adam Weiss