How Big Is a Blue Whale? Length and Weight Compared

How long is a blue whale?

A blue whale’s length depends on where it lives and whether it is male or female. Antarctic blue whales, the largest subspecies, are the longest: mature females there average about 25–27 m (83–87 ft). In the North Atlantic and North Pacific, mature females average around 21–24 m (69–79 ft). Off California, mature females average about 22 m (72 ft).

The longest blue whales measured by scientists reached about 29.9–30.5 m (98–100 ft). Whaling records include dozens of whales logged at over 30 m and a few at around 33 m (108 ft), but many researchers doubt these figures. Lengths were often taken quickly at whaling stations or on factory ships without standard methods, so errors and exaggeration are likely. A blue whale longer than about 30.5 m (100 ft) has never been confirmed.

How much does a blue whale weigh?

Weight is much harder to measure than length. No scale can hold a living blue whale, so almost all weights come from the whaling era, when dead whales were cut up and weighed piece by piece. Blood and other fluids were lost in the process, and researchers added an estimated allowance to the total.

Average weights differ by population. Northern Hemisphere males average roughly 100 tonnes and females about 112 tonnes. Antarctic males average around 112 tonnes and females about 130 tonnes. Pygmy blue whales are lighter, with males averaging roughly 75–100 tonnes. The heaviest blue whale on record was a female caught in the Southern Ocean in March 1947: she measured 27.6 m (91 ft) and was estimated at about 190 tonnes (210 short tons).

A 2024 study that modeled body shape suggested a 30 m (98 ft) blue whale could weigh around 184–205 tonnes, although other researchers think these figures are on the high side.

Male, female and pygmy blue whales

Like other baleen whales, blue whale females grow larger than males. A bigger body probably helps a mother store the energy needed to carry a calf for 10–12 months and then produce large amounts of milk.

The pygmy blue whale of the Indian Ocean and South Pacific has a shorter tail section, so it looks more tadpole-shaped than other blue whales. It is heavier for its length than other blue whales, and the largest pygmies reach about 24 m (79 ft).

How big is a baby blue whale?

A newborn blue whale is already one of the largest animals on Earth. It measures about 6–7 m (20–23 ft) and weighs 2–3 tonnes, about as much as a large SUV. Drinking its mother’s rich milk, it gains roughly 90 kg (200 lb) every day. By the time it is weaned at around 6–8 months old, it is about 16 m (53 ft) long.

Blue whale size compared with buses, elephants and planes

Numbers this large are hard to picture, so comparisons help:

• School buses: a full-size school bus is about 12 m (40 ft) long, so a typical adult blue whale is about as long as two buses parked end to end.
• Basketball court: the longest blue whales, about 30 m (98 ft), are slightly longer than an NBA court, which is 28.7 m (94 ft).
• Elephants: a big African bush elephant bull weighs about 6 tonnes, so a 130-tonne blue whale weighs as much as more than 20 bull elephants.
• Airliners: a Boeing 737-800 is 39.5 m (130 ft) long, so even the largest blue whale is about three-quarters of its length.

Inside, the scale continues. The heart weighs about 180 kg (400 lb), the heaviest of any animal, as explained in How big is a blue whale’s heart?

Is a blue whale bigger than a dinosaur?

As far as scientists know, the blue whale is the heaviest animal that has ever lived. Some giant sauropod dinosaurs, such as Argentinosaurus, may have been about as long, but most weight estimates for them fall around 65–80 tonnes, roughly half the weight of a big blue whale. These estimates come from incomplete skeletons, so they are uncertain.

In 2023 scientists described Perucetus, an early whale from Peru, and suggested it might have been heavier than a blue whale. Re-analyses published in 2024 and 2025 concluded that it was probably much lighter, and the blue whale keeps its title.

How does it compare with other whales and the whale shark?

The blue whale is far bigger than any other living whale. The fin whale, the second largest, reaches 26–27 m (85–90 ft) at most and usually much less. A large male sperm whale averages about 16 m (52 ft), and an adult humpback whale is 14–17 m (46–56 ft) and up to about 40 tonnes.

The largest fish, the whale shark, has been reliably recorded at up to 18.8 m (61.7 ft), well short of a big blue whale. See the full side-by-side in whale shark vs blue whale, or browse the largest animals in the world.