Size and Shape
Squids tend to be larger than calamaris. The narrower end of a squid's body has a pointed flap resembling an arrow while a calamari has long triangle-shaped flaps, reminiscent of wings, on each side.
Fins
Squids have short fins on the sides of their bodies. Calamaris, on the other hand, possess long fins that run the entire length of their bodies.
Use in Cooking
The tender flesh of a calamari cooks more quickly, which is suitable for fried, grilled or stir-fry dishes. Chefs are more likely to stuff squids or use them in stews.
Color
While there are color variations within both categories, calamaris tend to have some element of pink to their skin when fresh and uncooked, whether pink-purple or brownish pink. Squid flesh, on other hand, more often has a brownish cast, ranging from purpley-brown to a dark brownish green.