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Octopus vs. Squid (Key Similarities and Differences)

The main differences between octopuses and squids is that squids are bigger, heavier, have more limbs, and have a longer mantle than octopuses. They also have a gladius and different social life. Octopuses are smaller, lighter, have fewer limbs, and live alone. Both squids and octopuses are cephalopods, have the same amount of hearts and brains, and have the same diet. They are also venomous and die after mating.

It’s easy to see that octopuses and squids are quite similar. They have a lot of arms, their shape is kind of similar, and they both live in the water. 

But you may also spot a few differences between them.

In this article, we satisfy your curiosity with the octopus vs. squid comparison. We cover everything, including size, weight, limbs, anatomy, habitat, and social life.

Octopus vs. Squid Overview

Octopuses are smaller and lighter than squids. They also have rounder mantles, fewer and different limbs, while they don’t have a gladius. Octopuses are also exclusively solitarily. The two animals have similar taxonomy, brain and heart count, habitat, diet, and defense mechanisms.

It’s not surprising that squids and octopuses are related. They are both marine mollusks that roam the deep oceans and seas. But there is more than meets the eye.

Octopuses and squids differ in many important aspects:

  1. Size
  2. Weight
  3. Mantle
  4. Limb count
  5. Limb appearance
  6. Gladius
  7. Social life

Although different, they are related, so they are bound to share many similarities as well:

  1. Classification
  2. Brains
  3. Hearts
  4. Habitat
  5. Diet
  6. Venom
  7. Senescence
Octopus vs. Squid Overview

Differences Between Octopuses and Squids

Octopuses are smaller than squids, weighing up to 110 pounds compared to the 1,500 pounds mega squid. They also have fewer and different functioning limbs. Octopuses lack a gladius and live in solitary, while squids often live in schools.

SizeSmallest: smaller than an inch, largest: 14 feetSmallest: less than an inch, largest: 43 feet
WeightMaximum 110 poundsUp to 1,500 pounds
MantleOval and rotund Long and narrow
Limb CountEight limbsTen limbs
Limb AppearanceEight arms covered with suckersEight arms covered with suckers, two tentacles with suckers on the end
GladiusDoes not have gladiusHas gladius
Social LifeExclusively solitarySolitary or lives in schools


On one end of the extreme, octopuses and squids are similar in size. The smallest octopus, (the star-sucking pygmy octopus[1]) and the smallest squid (the Thai bobtail squid[2]) are both less than an inch long.

The real difference is seen amongst the largest species. 

The giant Pacific octopus rarely grows bigger than 14 feet while the largest squid (the giant squid) can exceed lengths of 43 feet.[4] Their mantle alone is seven feet; half the size of the giant Pacific octopus.


Differences Between Octopuses and Squids - Weight

On the low end of the weight scale, octopuses and squids are similar. The smallest species of both cephalopods rarely weigh more than 0.04 ounces.

The high-end differs greatly. The heaviest giant Pacific octopuses only reach weights of 110 pounds. The colossal squid (the heaviest squid species) is at least 1,100 pounds. 

The heaviest recorded individual was measured by fossil, and its estimated weight was about 1,500 pounds.[5]


Both octopuses’ and squids’ mantles serve the same function: contain the organs. Where they differ is appearance. Octopuses have oval and wide mantles. while squids have long and narrow mantles.

Another difference is that octopus mantles are squishy and floppy. When they are ashore, their mantle looks like a half-deflated ball.[6] Squids’ mantles are sturdier and hold their shape.

Limb Count

Differences Between Octopuses and Squids - Limb Count

Octopuses have eight limbs. Squids have ten limbs in total.

Although their limb count differs, both of them have the ability to detach and grow back limbs.

Limb Appearance

All eight of the octopus’ limbs look similar. They are long, muscular appendages, narrowing at the tip. The underside is covered with suckers, usually in two rows.

Eight of the squid’s limbs are similar to the octopus’, but two differ greatly. The two back limbs are much longer and only have suckers at the end. These are used to catch food.[7]

The difference between arms and tentacles is that arms have suckers on all of their length. Tentacles only have suckers at the tip. Therefore, octopuses have eight arms, while squids have eight arms and two tentacles. 


The gladius (or pen) is a structure made of chitin inside the squid’s mantle. It supports the muscular tissues and organs while being flexible to enable jet-propulsive swimming (filling the mantle with water and releasing it rapidly).[8]

Octopuses lack gladius and the only solid part of their body is their beak.

Social Life

Differences Between Octopuses and Squids - Social Life

Octopuses are exclusively solitary and territorial. They only have the intention to encounter another octopus if they want to mate. Otherwise, they only leave their dens to hunt.

Squid social life is dependent on species. Most species do prefer living alone, but others (especially the smaller ones) group up. These groups can have up to a million squids.

A group of squids is called a school.

Similarities between Octopuses and Squids

The main similarities between octopuses and squids are their classification, brains, hearts, habitat, diet, defense mechanisms, and senescence.

FeatureOctopus and Squid Similarity
ClassificationBoth are cephalopods
BrainsNine brains
HeartsThree hearts
HabitatEvery ocean and almost every sea
Defense MechanismsFleeing, ink squirting, autotomy, camouflage, venom
SenescenceBoth die after mating


Similarities between Octopuses and Squids - Classification

Both squids and octopuses are part of the class Cephalopoda. Cephalopod means “head-feet.” 

They are both invertebrate mollusks and both are considered exceptionally smart for their phylum.


Octopus and squid brains are complex systems of neurons. Both have a doughnut-shaped central brain wrapped around their esophagus. They also have eight mini-brains technically.

Each mini-brain controls an arm. These are dense collections of neurons running through the arms in structures called ganglia. These help them coordinate and give semi-autonomy to their limbs.


Squids and octopuses have three hearts. One main heart circulates blood in the body, while two branchial hearts are situated at the gills. The branchial hearts pump blood through the gills to oxygenate them.

They need three hearts to help circulation because their oxygen carrier, hemocyanin, is poor at transporting oxygen.


Similarities between Octopuses and Squids - Habitat

Octopuses and squids are found all over the marine world. Some species prefer warm and shallow waters, while others roam the bottoms of cold and deep oceans.


Squids and octopuses are carnivores. Diet varies slightly between the two, but all squid and octopus species generally prey on similar animals.

Both squids and octopuses include the following animals in their diet:

  • Small fish
  • Crabs
  • Lobsters
  • Clams
  • Snails

Additionally, both of them tend to be cannibalistic.

Defense Mechanisms

Similarities between Octopuses and Squids - Defense Mechanisms

Although they are predators, squids and octopuses have many ways to defend themselves. Both of their first instinct is to flee when sensing danger. They only turn offensive if their predator is persistent in chasing them.

Apart from fleeing, octopuses and squids use the following for self-defense:

  • Rapid swimming speed
  • Ink squirting
  • Camouflage
  • Autotomy
  • Venom


Like all cephalopods, octopuses and squids only mate once and die after. The reproduction is followed by a life stage called senescence.

It is characterized by self-destructive behavior: mothers stop feeding and tear chunks out of themselves, and fathers behave erratically and put themselves in harm’s way.[9]

How to Tell the Difference Between Octopuses and Squids

You can tell the difference between octopuses and squids by their appearance, limb count, and size.

It is easy to differentiate between octopuses and squids. The most apparent difference is their appearance. Octopuses have oval and plump mantles, while squids have long and narrow ones.

You can tell whether you’re looking at an octopus or a squid by their limbs: If you count eight, it’s an octopus. If you count ten, it’s a squid. 

Squids also have two longer appendages called tentacles, which only have suckers on their ends.

Size is also a differentiating factor. While smaller octopuses and squids are similar, the biggest ones are different. The largest octopuses are rarely bigger than 14 feet, while squids can be 43 feet long.

How to Tell the Difference Between Octopuses and Squids

Octopus vs. Squid: Who Would Win in a Fight?

Octopuses and squids are evenly matched. The outcome of a fight heavily depends on who fights and where they fight.

A fight between the two species would be a toss-up. Both have their specific pros and cons.

Pros and ConsOctopusSquid
ProsMuscular build, higher intelligence, flexible body, maneuverability, more potent venomSturdier mantle, more tentacles, heavy size and weight advantage, fast swimmer, sharp eyesight
ConsClumsier movement, slower swimmer, delicate mantleCan’t fit into tight spaces, less maneuverability

The outcome heavily depends on who attacks first, what species fight, and where they fight. Octopuses would probably win in tighter spaces, but in open water, the generally bigger squids can overpower them.

Although squids and octopuses meet in the wild, neither of them is generally interested in fighting. They prefer smaller prey.


The difference between octopuses and squids is that octopuses are generally smaller and lighter than squids. They also have fewer and different limbs, different mantles, and different social life.

Octopuses and squids are similar in classification, habitat, and diet. They have similar hearts, brains, and defense mechanisms. Both mate only once and die after. A fight between an octopus and a squid would be evenly matched.

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The Misfit Animals staff consists of animal lovers, pet enthusiasts, veterinarians, zoologists, and other animal experts. Our goal is to provide people with information on proper animal care.

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