Nobody knows for sure the exact size for each theropod, but here are most of the contestants for the largest ones.
- Spinosaurus aegyptiacus was likely one of, if not the, largest theropod of all. With most modern estimates of 12-18 meters in length and a very uncertain weight, it is usually known as the largest but may or may not actually be since there might be new dinosaurs found and is bigger in the future.
- Acrocanthosaurus atokensis was one of the largest terrestrial predators ever at 11.6-12 meters in length and about 6.2 tons in weight. Its' behind T. rex of the largest North American carnivore ever.
- Giganotosaurus carolinii was another giant carcharodontosaurid, but on average lighter than Carcharodontosaurus. The average size is under dispute but somewhere around 12.5-14 meters or probably even longer. If was once thought to be the biggest theropod dinosaur, but Spinosaurus is possibly larger than this. It also had the largest skull of any carnivorous dinosaur along with C. saharicus (1.6 meters).
- Oxalaia quilombensis has a very uncertain size. What we know about it is it was most likely a large spinosaurid similar to Spinosaurus, though size estimates range anywhere from 11-14 meters, and it may be possible it didn't even fall within that size range. It is pretty obvious that it was a large theropod though, but it is hard to compare based on its fragmentary remains. It probably is lighter then the others such as T. rex, Carcharodontosaurus, Spinosaurus and others.
- Saurophagnax maximus It was a large allosaurid from the late Jurrasic. It is very similar to Allosaurus. In fact it can be the adult form of Allosaurus (A. maximus).It's size was around 10.5-14 meters. Despite being so large it was very rare. Only accounting 1% of the Morrison formation.
- Carcharodontosaurus saharicus It was a large carcharodontosaurid living along side Spinosaurus, Suchomimus, Sarcosuchus and Bahariasaurus. One of the largest carcharodontosaurid. It could have reached 13.6 meters. It can be a competition for Spinosaurus. It had the largest skull of any carnivorous dinosaur (1.6 meters).
- Tyrannosaurus rex It was the largest tyrannosaurid ever having a 1.5 meter skull and reaching 12-13 meters long and 6-7 tons. Though stock, it is among the largest carnivorous dinosaurs of all time.
- Bahariasaurus ingens It was the largest ceratosaurid reaching up to 13.6 meters. Very little is known about this dinosaur because all remains were fragmentary. But paleontologists somehow managed to figure out it's size. It is very closely related to Deltadromeus. And it is possible that they are synonymous.
- Carcharodontosaurus iguidensis After the remains of C. saharicus in World War || were destroyed it was discovered, in 2002. It is smaller than C. saharicus, but still a large dinosaur. It's size should have been 10-13.6 meters. But it's weight is exceptionally less with C. saharicus around 8 tons and it only being 4.5 tons.
- Tyrannotitan chubutensis It is a large carcharodontosaurid and the most recently discovered. It was discovered in 2002. Only a few fragments have been found and it showed a size of 12-13.3 meters.
Chilantaisaurus tashuikouensis It is a neovenatorid from China. Very little is known. It could reach sizes up to 13 meters. It is very uncommon to public. This is the largest neovenatorid.
Allosaurus fragilis It can hardly reach up to 11 meters. Though the research done by Gregory S. Paul in 2016 which revealed many juicy secrets about dinosaurs showed that it can reach sizes of 13 meters. Nature doesn't deceive us we deceive ourselves.