Biggest Animals in the World, Alive and Extinct: A Size Comparison

"Biggest" sounds like a simple word until you try to rank animals by it. Longest, tallest and heaviest give three different lists, the record-holders are often known from one stranded body or a handful of fossil bones, and the figures that get repeated tend to be the largest anyone ever claimed. So the honest answer to "how big was it?" is usually a range, with a story about how the range was reached.

The giants of land and sea are some of the most satisfying rounds in Scale of Things, because almost everyone guesses them too small. The game measures animals as a typical large adult, mostly by length. Here is how the biggest compare, and why their numbers are argued over.

Length, height and weight rank animals differently, and it is worth being clear which one you mean.

• By weight, the blue whale has no rival alive and probably none in the fossil record.
• By length, the longest sauropod dinosaurs were longer than any whale, and some stringy sea creatures are longer still.
• By height, the giraffe wins among the living, and long-necked sauropods won among the extinct.

A shape on a board shows length and height, not weight, which is why a slender dinosaur and a bulky whale can be close on the board and far apart on a scale.

The blue whale is the largest animal known to have lived. The longest reliably measured were around 30 metres, and the heaviest recorded came close to 200 tonnes. Whaling-era reports of 33 metres and more exist, but many were measured along the curve of the body or in ways that are now hard to check, so most scientists treat them with caution. A big adult is usually somewhere in the mid twenties of metres.

In the game the blue whale is 27 m long, about as long as a basketball court, and its heart has a round of its own at 1.5 m tall, about half the height of a basketball hoop.

Its title was challenged in 2023, when a team led by Giovanni Bianucci described Perucetus colossus, an ancient whale from Peru whose bones are so dense and heavy that they estimated it might have matched or exceeded the blue whale in weight. In 2024 Ryosuke Motani and Nicholas Pyenson reworked the estimate and argued for a far lower figure, under that of a large blue whale. The animal is known from part of a skeleton with no skull, which is exactly the kind of evidence that leaves room for argument.

The longest animals that ever walked were the titanosaurs and their long-necked relatives. Argentinosaurus, from Argentina, is the usual headline: estimates run from about 30 to 35 metres long and from roughly 50 to 100 tonnes. The game has it at 32.5 m, longer than its blue whale. But Argentinosaurus is known from only a handful of bones, some vertebrae, ribs and part of a leg, so every figure is a reconstruction from its relatives.

Patagotitan, described in 2017, is better known, from several partial skeletons, and comes out at around 31 metres and something like 50 to 70 tonnes. Further down the game's list, Diplodocus stands at 25 m and Brachiosaurus at 23 m. Their length is mostly neck and tail, so on the board they look lighter than they were.

The most famous case of an inflated sauropod is a bone nobody can measure any more. In 1878 the palaeontologist Edward Drinker Cope described a single enormous vertebra, later lost. Scaled up from its relatives, it was once said to belong to an animal of nearly 60 metres. In 2018 Kenneth Carpenter reassessed Cope's drawings and measurements, placed the animal in a different family of sauropods with taller vertebrae, renamed it Maraapunisaurus, and brought the estimate down to around 30 metres.

How do scientists weigh an animal that is a few bones? Two ways, broadly. One scales up from the thickness of the main limb bones, which carry the weight: Nicolás Campione and David Evans showed in 2012 that limb bone circumference predicts body mass well across living four-legged animals. The other builds a digital model of the body around the skeleton and estimates its volume. The two methods often disagree by tens of percent, which is why the ranges are so wide.

The extinct shark Otodus megalodon is known almost entirely from teeth, plus some vertebrae, because shark skeletons are cartilage and rarely fossilise. Its teeth are the giveaway: the largest are about 18 cm tall, and the game has one as a round of its own. Lengths are estimated by scaling from teeth and vertebrae to living sharks, and the answer depends on which shark you assume it resembled.

Estimates for the largest individuals have mostly fallen between about 15 and 18 metres, and recent work arguing that megalodon was more slender than a great white has pushed some estimates past 20 metres. The game's megalodon is 16 m, and its great white shark 5 m: more than three times as long, which is exactly the kind of gap where a guess stops short.

The giant squid is the classic case of a size that grows in the retelling. A big female reaches around 12 to 13 metres at most, and most of that is the two long feeding tentacles; the body itself, the mantle, is about 2 metres. Claims of 18 or 20 metres come from stranded animals whose tentacles had stretched like rubber after death. Its relative the colossal squid is shorter but much heavier.

If you want the longest animals of all, the answers get stranger. The lion's mane jellyfish has trailing tentacles that can reach tens of metres; the largest recorded, found in Massachusetts Bay in 1870, was said to have tentacles over 36 metres long. The bootlace worm has been reported at 55 metres, though it stretches so easily that the figure means little. Some siphonophores, colonies of linked bodies drifting in the deep, stretch tens of metres too. None of them comes close to a whale in weight.

The African bush elephant is the largest land animal alive. A big bull stands over 3 metres at the shoulder and weighs 6 tonnes or more. The largest on record, shot in Angola in 1955 and on display at the Smithsonian's natural history museum since 1959, stood nearly 4 metres. The game measures its African elephant by length, 7.2 m, which surprises people who picture an elephant as tall rather than long.

Some extinct relatives were bigger still. The straight-tusked elephants of the genus Palaeoloxodon may have been far heavier than any elephant alive, and the hornless rhinoceros relative Paraceratherium was taller at the shoulder than any elephant today, though the biggest estimates for both rest on few bones. The game's mammoth, at 6 m long, is exactly the length of its Asian elephant: woolly mammoths were roughly the size of elephants alive today, not the towering beasts of films.

A few more giants that turn up in the game, with honest ranges:

• Giraffe: the tallest living animal, with big males reaching about 5.5 metres. The game's giraffe is 5 m tall.
• Whale shark: the largest fish. Adults commonly reach 10 metres or more, with reports of individuals near 18. The game's is 8 m long.
• Saltwater crocodile: the largest living reptile. Big males pass 6 metres, and the largest measured in captivity, Lolong in the Philippines, was 6.17 m. The game's is 4.75 m.
• Ostrich: the largest living bird, up to about 2.7 metres tall. The game's is 2.45 m.
• Quetzalcoatlus: the giant pterosaur, with a wingspan of about 10 to 11 metres, measured across in the game at 10.5 m. The wandering albatross, the living bird with the widest wings, spans up to about 3.5 metres.

Almost every argument about a giant comes down to the same few causes.

1. Typical or record? A typical adult and the largest ever measured can differ by a third or more, and the record is the figure that gets repeated.
2. How it was measured. Along the curve or in a straight line, with or without the tail, tentacles relaxed or stretched.
3. What survived. A fossil known from a few bones has to be scaled from its relatives, and the choice of relative moves the answer.
4. Length or mass. A long, thin animal and a short, heavy one can trade places depending on which you rank by.

When the game shows a size, it is a typical large adult, so the record figures in your head will usually overshoot. Our guide to getting better at Scale of Things explains what each round's measurement covers. And because the score is a ratio, being off by 10 metres on a whale costs far less than it sounds: what matters is the factor, a habit of thought that the powers of ten make second nature.

Next time a whale or a dinosaur stands beside a bus, count buses, then push your guess a little further than feels right.