Octopus vs Squid

Octopus and squid are both cephalopods, soft-bodied mollusks with a beak and a ring of limbs around the mouth. They are often sold in the same case at a fish market, and menus use confusing names. The anatomy is easy to read once you know what to look for: limbs, fins and what holds the body together.

An octopus is a rounded, flexible animal that mostly crawls along the seafloor. A squid is a streamlined, torpedo-shaped swimmer that moves by jet propulsion. Neither has an outer shell, but a squid carries a thin chitin rod called a pen inside the mantle, and an octopus does not.

Octopus vs Squid side by side

Last verified October 2026. Typical values; individual animals, products and local prices vary.

When you are looking at which

Octopus

• You count eight limbs of equal length and no longer pair.
• The body is rounded and baggy, with no fins on either side of the head.
• The animal is crawling or squeezing into a crevice on the bottom.
• Cut open, there is no hard rod inside the body.

Squid

• You see two extra limbs, longer and thinner, with suckers only at the tips.
• The body is long and pointed, with triangular fins along the mantle.
• The animal is jetting through open water, tail first.
• Cleaning it reveals a clear, plastic-like rod inside the body.

How this works

This page compares the two animals on anatomy that marine science references agree on: limb count, tentacles, internal pen, fins, body shape and movement. The quiz asks five questions you can answer from a photo, a video, a tank or a whole animal at a market.

Dead or frozen animals can lose their tentacles, so a missing tentacle is not proof of an octopus. Use the pen and fin cues together with the limb count, and look at the whole animal rather than a single piece before deciding.

Where these numbers come from

The figures and defaults on this page are based on:

• Smithsonian Ocean: Cephalopods, Arms, tentacles, pen and movement differences between octopus and squid (checked October 2026)
• Wikipedia: Octopus, Eight limbs, hearts, lifespan, lack of fins and flexible body (checked October 2026)
• Wikipedia: Squid, Arms, tentacles, gladius, fins and typical Loligo lifespan (checked October 2026)

Field-identification guide. Damaged specimens and other cephalopods can look similar and are not covered.