The holotype of the type species, Futalognkosaurus dukei, was originally estimated at  in length. In 2008 this was downsized to . In 2012 Holtz estimated it at  long and with an approximate weight of 43.5 to 51 tonnes (48-56 short tons).
The holotype of the type species, Futalognkosaurus dukei, was initially estimated to be  in length. In 2008, this measurement was reduced to . In 2012, Holtz estimated it at  long and with an approximate weight of 43.5 to 51 tonnes (48-56 short tons).