Tyrannosaurus
Size

T. rex was one of the largest land carnivores of all time. One of its largest and the most complete specimens, nicknamed Sue (FMNH PR2081), is located at the Field Museum of Natural History in Chicago. Sue measured 12.3–12.4 m (40.4–40.7 ft) long, was 3.66–3.96 meters (12–13 ft) tall at the hips, and according to the most recent studies, using a variety of techniques, maximum body masses have been estimated approximately 8.4–8.46 metric tons (9.26–9.33 short tons). A specimen nicknamed Scotty (RSM P2523.8), located at the Royal Saskatchewan Museum, is reported to measure 13 m (43 ft) in length. Using a mass estimation technique that extrapolates from the circumference of the femur, Scotty was estimated as the largest known specimen at 8.87 metric tons (9.78 short tons) in body mass.

Not every adult Tyrannosaurus specimen recovered is as big. Historically average adult mass estimates have varied widely over the years, from as low as 4.5 metric tons (5.0 short tons), to more than 7.2 metric tons (7.9 short tons), with most modern estimates ranging between 5.4 and 8.0 metric tons (6.0 and 8.8 short tons).

A 2024 study estimated based on allometry that world-record sized T. rex specimens (1 in 100,000 individuals) may have reached lengths and weights exceeding 15 m (49 ft) and 15,000 kg (33,000 lb) respectively, though no individuals close to this size have ever been found. The study also found that there was little evidence of size-based sexual dimorphism in T. rex.
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