Both of these whale species are incredibly large but, when measured up against one another, the blue whale is almost twice as large as the sperm whale and nearly triple the weight.

Sperm whale diving with calfBlue whale diving back into the depths of the ocean
Sperm Whale (left) vs Blue Whale (right) Visual Comparison

Credit: Credit (left): Gabriel Barathieu

The Main Differences Between a Sperm Whale and Blue Whale

Here are the top five main differences between the basking shark and the sperm whale: 

  • Size: Sperm whales can grow to 67 feet, which is around 20 feet shorter than blue whales. See a Blue Whale size comparison here.
  • Appearance: Sperm whales have a ‘blocky’ head with an S-shaped blow hole. The blue whale is, on the other hand, long and slender and has a much larger mouth.
  • Habitat: Sperm whales live in deep oceans globally, whereas blue whales live in all oceans except the Arctic.
  • Diet: Sperm whales eat squid/octopus and rays. Blue whales eat krill, as they are filter feeders.
  • Life span: Sperm whales live to around 70 years, whilst the blue whale can live between 80-90 years.

We’ll explore these differences and interesting facts about each whale more below.

Sperm Whale 

The sperm whale is the third deepest diving mammal globally and has the largest brain of any animal. The name comes from the oil spermaceti, that’s a target of whalers. 

Sperm whale diving with calf
Sperm whale diving with calf


The sperm whale is one of the largest whale species in the world. It can grow to around 67 feet (around 20 feet shorter than the blue whale) and live to 70 years of age and longer.

Sperm whale skeleton
Sperm whale skeleton

The sperm whale has a unique appearance making it hard to mix up with other specimens. It has a large, blocky head that takes up a great deal of the animal’s total length. The blowhole is S-shaped and located close to the front of the head. It would be quite difficult, after becoming familiar with both blue and sperm whales, to mix the two up. 


Sperm whales live around all deep oceans, from the equator to the edge of the Arctic and Antarctic ice packs, according to NOAA. The whale population is still recovering from commercial whaling in the 19th and 20th centuries, which decreased their populations substantially. 

Usually, sperm whales are found far from the land. They prefer to hunt in deeper waters. 


Sperm whales can dive between 300-800 meters or 980-2,620 feet in search of food. These dives may last up to an hour. They eat everything from squid to octopuses and rays. Much of what scientists know about some deep-sea creatures, like the deep-sea squid, has been determined based on remains in sperm whales’ stomachs. Some evidence suggests that their teeth are used as weapons when one male fights another.


sperm whale on beach
View of sperm whale teeth and upper sockets

Facts about Sperm Whales 

  • Interestingly, the sperm whale also has the largest brain of any known living or extinct animal on Earth. It weighs around 17 pounds or 7.8 kilograms. 
  • The whales are currently listed as vulnerable by the IUCN. 
  • Male sperm whales become sexually mature around 18 years of age, and female sperm whales are fertile at around nine years of age.
  • The sperm whale is one of the largest whale species in the world.

Blue Whale 

These whales are considered to be the largest known animals to have ever lived on Earth. There have been a total of 88 whales longer than 98 get and one reaching 108 feet, according to the IWC.

Due to its size, the only real natural threat the blue whale faces comes from the orca, which is known to work in groups to attack blue whales. The calves are far more threatened by orcas than full-grown adults. The largest confirmed sighting of a blue whale was 29.9 meters or 98 feet with a weight of 173 tonnes.

Blue whale diving back into the depths of the ocean
A Blue Whale diving back into the depths of the ocean

Blue whales have a famous method of communication. According to National Geographic, they emit a series of pulses and groans that can be heard by other whales up to 1,000 miles away. These sounds can be used to tell blue whale groups apart.


Depending on the animal, the whale can vary between shades of blue and grey. They have long slender bodies that appear blue underwater. Their bodies also feature unique mottling patterns on their backs and pigmentation around the dorsal fin, as described by “Photographic identification of the blue whale in the Gulf of St. Lawrence, Canada.”

The blue whale is the largest animal on Earth
The blue whale is the largest animal on Earth


Blue whales live in every ocean except the Arctic. They usually live alone or in pairs and spend their winters migrating toward the Equator. This improves their access to prey in the winter and may, according to Biology Letters, reduce parasitism and pathogens. 

Blue whales can be found in North Atlantic Ocean, from the subtropics to the Greenland Sea, as well as off the coast of the eastern United States and Canada. North Pacific blue whales live around the western coast of the United States.

They migrate to Central America during the winter. There is also a population of whales in the Indian Ocean, with sightings retried in the Gulf of Aden, Arabian Sea, and other smaller bodies of water (NOAA). 


Famously, the largest animal on Earth eats one of the smallest. Blue whales primarily eat krill but have also been documented eating crustaceans and fish. They filter feed, meaning that they swim towards large groups of krill with their mouths open (this is different from how sperm whales eat). The blue whales push the water out of their mouths with their tongue and swallow the krill, according to NOAA. 

Facts about Blue Whales 

  • The blue whale is the largest animal to ever live on Earth. 
  • They communicate through vocalizations. 
  • Blue whales are also the loudest animals on Earth.
  • Blue whales live for around 80-90 years.
  • Blue whale calves are around three tons and 25 feet long when they’re born.
  • The mother-calf bond is the strongest in the whale community.


Is a sperm whale bigger than a blue whale?

No, blue whales are significantly larger than sperm whales. They can be up to twice as large and three times as heavy. 

Do sperm whales eat humans?

There are no clear or reliable reports of a sperm whale ever eating a human being. Their prey is located miles beneath the surface and includes squid and octopuses. 

Can sperm whales vibrate you to death?

It’s possible, due to their size that, they might crush a swimmer’s body accidentally with their bodies or tails. They also, some scientists believe, “vibrate” one’s body to death. This is due to their loud vocalizations. They’re considered to be the loudest animals on the planet. 

Do blue whales still exist? 

Yes, despite threats to their population numbers since the 1800s, blue whales still live in the Earth’s oceans. There are believed to be as many as 250,000 whales in the world’s oceans (still making it one of the world’s rarest species). 

Are blue whales friendly to humans?

Blue whales are enormous animals, meaning that they always pose a threat to humans in the water. But, they are not predatory. They have no interest in hurting or eating human beings. Many divers have experienced swimming near these large creatures. 

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