It's about one-and-one-tenth times as heavy as The Space Shuttle.
In other words, the weight of The Space Shuttle is 0.910 times 81 tonnes.(for Endeavour, a.k.a. OV-105, a.k.a. Orbiter Vehicle-105) (empty weight, excluding main engines)
When empty, the space shuttle Endeavour weighs 71 tonnes. The shuttle's spacious cargo bay carried the Chandra X-ray Observatory into orbit in 1999 — a payload that weighed 20 tonnes.
It's about three-fourths as heavy as a Blue Whale.
In other words, 81 tonnes is 0.7750 times the weight of a Blue Whale, and the weight of a Blue Whale is 1.290 times that amount.(Balaenoptera musculus)
Blue whales weigh between 105 tonnes. The largest mammal to have ever lived, blue whales feed almost exclusively on krill — tiny invertebrates weighing about 0.000001000 tonnes each.
It's about half as heavy as a House.
In other words, 81 tonnes is 0.5190 times the weight of a House, and the weight of a House is 1.930 times that amount.(149 sq. m, single-level, unfurnished)
A 149 sq. m (1,600 sq. ft), single-story, unfurnished house (without extensive masonry) of the type commonly found in America would weigh approximately 156 tonnes, based on the weight of the included materials. In contrast, a yurt — a type of dwelling structure popular among nomadic peoples of East Asia — typically weighs less than 0.460 tonnes.
It's about seven times as heavy as an Anchor of a Cruise Ship.
In other words, 81 tonnes is 7.170 times the weight of an Anchor of a Cruise Ship, and the weight of an Anchor of a Cruise Ship is 0.1390 times that amount.(for QE2 forward anchor, a.k.a. RMS Queen Elizabeth 2)
Each of the forward anchors of the RMS Queen Elizabeth 2 weighs 11.30 tonnes. The anchor of the QE2 now sits in front of the Holyrood Church in Southampton, England, United Kingdom, along a pedestrian tourist route known as "the QE2 mile."
It's about one-tenth as heavy as Christ the Redeemer (statue).
In other words, 81 tonnes is 0.1280 times the weight of Christ the Redeemer (statue), and the weight of Christ the Redeemer (statue) is 7.810 times that amount.(a.k.a. O Cristo Redentor, a.k.a. Christo redemptor) (Rio de Janeiro, Brazil)
Christ the Redeemer weighs 635 tonnes. The statue overlooks the city of Rio de Janeiro from atop the 709.9-meter (2,329 ft) granite peak in the Tijuca Forest National Park.
It's about thirteen times as heavy as a Tyrannosaurus rex.
In other words, the weight of a Tyrannosaurus rex is 0.077 times 81 tonnes.(for FMNH PR2081, a.k.a. "Sue") (a.k.a. Tyrannosaurus, a.k.a. T-Rex) (estimated live weight)
The notable Tyrannosaurus specimen housed at the Field Museum of Natural History in Chicago, Illinois, "Sue," is estimated to have weighed about 6.4 tonnes while alive. A renowned predator in popular culture, the teeth of tyrannosaurus rex were up to 33.02 cm (13 in) long.
It's about thirteen times as heavy as an Elephant.
In other words, the weight of an Elephant is 0.077 times 81 tonnes.(for African bush elephant, Loxodonta africana) (Adult, bull)
A bull African bush elephant weighs about 6.10 tonnes. Among African elephants, both males and females have tusks (whereas female Asian elephants, Elephas maximus, do not have tusks) which can grow to 3 m (10 ft) and typically weigh about 4 tonnes