A blue whale is the biggest animal known to have lived. The largest, around Antarctica, reach about 33 m (108 ft), the longest reliably measured. They weigh up to about 150 tonnes (330,000 lb), says NOAA Fisheries. Blue whales in the North Atlantic and North Pacific are smaller, growing to about 27 m (90 ft).
That is about as long as 17 adult men lying head to toe, and as heavy as about 1,650 of them. Size depends a lot on where a blue whale lives, and whether it is male or female. Females are usually a bit bigger than males, according to NOAA Fisheries. So the honest answer is a range, not one number.
How big is a blue whale? Sizes by population
| Group | Length | Weight | Source |
|---|---|---|---|
| Antarctic blue whale | Up to about 33 m (108 ft) reliably measured; NOAA rounds to 110 ft | Up to about 150 t (330,000 lb) | NOAA Fisheries; McClain et al. 2015 |
| North Atlantic and North Pacific | Up to about 27 m (90 ft) | Over 45 t (100,000 lb) | NOAA Fisheries |
| Pygmy blue whale (Indian Ocean and around Australia) | Up to 24.1 m (79 ft) | No reliable figure found | Australian Government |
| Longest reliable record | 33 m (108 ft), measured by whalers | No whole blue whale has ever been weighed | McClain et al. 2015 |
| Heaviest estimates | Not applicable | 190 and 199 t (whalers’ estimates); about 270 t (2024 calculation) | McClain et al. 2015; Motani & Pyenson 2024 |
| Newborn calf | About 7 m (23 ft) | 2.3–2.7 t (5,000–6,000 lb) | US National Park Service |
| Calf at weaning (6 months) | Over 15.8 m (52 ft) | Not given | US National Park Service |
The pygmy blue whale is a smaller subspecies, which explains much of the size difference between regions. The Australian Government records it growing to 24.1 m, while Antarctic blue whales grow to over 30 m.
How long is a blue whale in feet and metres?
You’ll often see “110 feet” or “33.58 metres” given as the record. That 33.58 m whale was measured more than a century ago, and scientists don’t fully trust it. A 2015 review in PeerJ, led by Craig McClain, looked at whaling records. It gives 33 m (about 108 ft) as the longest reliable length, from a whale caught in Antarctic waters in 1930.
Why the doubt? Some early whalers may have measured in Norwegian feet, which are slightly longer than ordinary feet. They may also have measured along the curve of the body rather than in a straight line. The review found that most caught whales were much smaller: 95% were shorter than 27.1 m (about 89 ft).
So “up to about 30 m (100 ft)” is a fair everyday answer. “Up to 33 m (108 ft)” is the top end for rare Antarctic giants.
How much does a blue whale weigh?
Weighing a blue whale is much harder than measuring one. According to the 2015 PeerJ review, no complete blue whale has ever been weighed in one piece. Here is what we have instead:
- NOAA’s figure: up to 330,000 lb (about 150 tonnes) for the biggest Antarctic whales. The National Park Service gives about 160 US tons (145 tonnes) for a 30 m (100 ft) adult.
- Whalers’ estimates: the two highest are 190 and 199 tonnes. Whalers cut whales into pieces, added up what went into their cooking tanks, and guessed how much blood was lost.
- A formula: in 2024, Ryosuke Motani and Nicholas Pyenson calculated that the largest blue whales could have weighed about 270 tonnes, reports UC Davis. That number comes from maths, not a scale.
The old claim that blue whales “weigh up to 200 tons” sits at the very top of these estimates. It isn’t a typical weight.
How big is a blue whale compared to a human?
The average US man is 175 cm (5 ft 9 in) tall and weighs 90 kg (199 lb), says the CDC. You would need about 17 of them lying head to toe to match a 30 m (100 ft) blue whale. The average US woman is 161 cm (5 ft 3.5 in), so it would take about 19 women.
Weight is even more lopsided. A 150-tonne whale weighs about as much as 1,650 average men, or about 1,900 average women (78 kg, or 172 lb, each).
| Compared with | Its size | How it stacks up |
|---|---|---|
| Average US man | 175 cm (5 ft 9 in), 90 kg (199 lb) | About 17 men long; about 1,650 men in weight |
| SUE, the largest known T. rex | More than 12 m (40 ft) long | About 2.5 SUEs nose to tail |
| Adult Asian elephant | 2,750–5,420 kg (6,000–12,000 lb) | About 28 to 55 elephants in weight |
| Newborn blue whale calf | About 7 m (23 ft) | About 4 calves long |
| Boeing 737-8 airliner | 39.5 m (129 ft 6 in) | The plane is about 9.5 m (31 ft) longer |
Comparisons are rounded. Other sizes are from the Field Museum, Smithsonian’s National Zoo and Boeing.
Is the biggest blue whale longer than a 737? No. Even the shortest current model, the 737-7, is 35.6 m (116 ft 8 in) long. The longest reliably measured blue whale, at 33 m, would fit along it with room to spare.
How big are baby blue whales, and how fast do they grow?
A newborn blue whale is about 7 m (23 ft) long and weighs 2.3 to 2.7 tonnes (5,000 to 6,000 lb), says the US National Park Service. That’s roughly four adults lying head to toe, and close to the weight of a small adult Asian elephant.
On its mother’s rich milk, a calf gains up to 4.5 kg (10 lb) an hour, or over 113 kg (250 lb) a day. It is weaned at six months old, when it is already over 15.8 m (52 ft) long. Blue whales can live about 80 to 90 years, NOAA estimates, and become adults at 5 to 15 years old.
How big is a blue whale’s heart?
You may have heard that a blue whale’s heart is “the size of a car”. The Royal Ontario Museum preserved the heart of a whale that died in ice off Newfoundland in March 2014. The museum calls it the largest heart of any animal on Earth.
Press reports give its weight as about 180 kg (400 lb), without blood. It has been compared to a Smart car, one of the smallest cars on the road. So “car-sized” is fair only if you mean a very small car.
That giant heart beats very slowly. In a 2019 study in PNAS, Jeremy Goldbogen’s team stuck a heart-monitoring tag to a wild blue whale with suction cups. On feeding dives as deep as 184 m (604 ft), its heart usually beat 4 to 8 times a minute, and sometimes only twice. At the surface it sped up to 25 to 37 beats a minute, close to the fastest scientists think it can go.
Was any animal ever bigger than a blue whale?
Not as far as we know, and that includes every dinosaur. In 2023, a fossil whale from Peru called Perucetus colossus challenged the title. Its first mass estimate was about 180 tonnes, within a range of 85 to 340 tonnes.
In 2024, Motani and Pyenson re-ran the numbers, UC Davis reports. They estimated that a 17 m Perucetus weighed 60 to 70 tonnes, perhaps over 110 tonnes if it grew to 20 m. That is well below the biggest blue whales, so for now the blue whale keeps the crown.
Why are blue whales so big?
Blue whales eat tiny shrimp-like animals called krill. The biggest may eat up to 6 tons of krill a day, according to NOAA Fisheries. Krill gather in huge, dense swarms, but the swarms can be far apart.
The PeerJ review links giant size to filter feeding on plankton. A huge body can take in enormous mouthfuls and store lots of energy as blubber for long trips between feeding areas. To see how the mouth manages it, read how long a blue whale’s tongue is.
Being huge didn’t protect blue whales from people. Commercial whaling killed hundreds of thousands, and NOAA lists the blue whale as Endangered under the US Endangered Species Act. The IUCN also lists it as Endangered.
Want to compare other giants? See how big whale sharks are, the biggest fish, or how much a beluga whale weighs. You can also find out what happens when a whale dies.
Frequently asked questions
How big is a blue whale in feet?
Northern blue whales grow up to about 90 feet. The largest Antarctic blue whales reach about 100 to 108 feet, and NOAA rounds the top figure to 110 feet. In whaling records, 95% of blue whales were under about 89 feet.
Are female blue whales bigger than males?
Yes. As in many baleen whales, female blue whales are generally larger than males, according to NOAA Fisheries. A bigger body may help a mother carry a calf for 10 to 12 months and then feed it rich milk until it is weaned at about six months.
Is a blue whale bigger than a dinosaur?
Yes. SUE, the largest known T. rex, is more than 12 m (40 ft) long, less than half a big blue whale's length. Some long-necked dinosaurs were longer than blue whales, but their bodies were much lighter. No dinosaur is known to have come close to a blue whale's weight.
How do scientists know how big blue whales are?
Most length records come from whalers, who measured tens of thousands of whales in the last century. Weights are harder: no whole blue whale has ever been weighed. Scientists combine whalers' records, measurements of stranded whales, and formulas that estimate weight from length.
Sources
- NOAA Fisheries. Blue whale (Balaenoptera musculus) species profile.
- PeerJ (PubMed Central copy) (2015). Sizing ocean giants: patterns of intraspecific size variation in marine megafauna (McClain et al.), DOI 10.7717/peerj.715.
- US National Park Service. Blue whale.
- Australian Government Department of Climate Change, Energy, the Environment and Water. Balaenoptera musculus: Blue Whale, Species Profile and Threats Database.
- NOAA Institutional Repository (2019). Extreme bradycardia and tachycardia in the world's largest animal (Goldbogen et al.), PNAS 116(50): 25329–25332, DOI 10.1073/pnas.1914273116.
- Royal Ontario Museum. Blue whale heart arrives at the ROM.
- University of California, Davis (2024). Slimming down a colossal fossil whale (on Motani & Pyenson, PeerJ 2024).
- CDC National Center for Health Statistics. FastStats: body measurements (2021–2023 data).
- Boeing. 737 MAX.
- Field Museum. SUE the T. rex.
- Smithsonian's National Zoo and Conservation Biology Institute. Asian elephant.
Sources checked 15 September 2026.
Keep the conversation curious