How Big Do Hermit Crabs Get? (6 Largest Hermit Crabs)

Does it ever fascinate you how different creatures can be so adaptable to their surroundings? Take, for instance, hermit crabs. Living in shells that have incredibly different shapes and sizes may lead you to question how big hermit crabs get.

These tiny crabs are now becoming popular pets that some people adore. Perhaps you, as well, like to have a hermit crab of your own in the near future. Although it might be a lot of fun, it’s best to first familiarize yourself with them.

This article will walk you through the largest hermit crabs ever discovered to give you an idea of how big these adorable and social creatures can get.

Biological Description

Hermit crabs, generally, are all nocturnal creatures that carry their home on their backs like snails. However, these crabs don’t have their own shells when they are born. They basically take other crabs’ shells or other hollow items as a refuge for the protection of their body, making them nature’s bandits.

Without a protective shell, which their bodies lack, they are very susceptible to predators. They need to find a shell to protect their soft, exposed abdomen.

Hermit crabs’ bodies can fit within these borrowed shells thanks to their tail that can be curled and also comes with a hook. When a hermit crab outgrows its shell exoskeleton, it will dig through sand and molt, looking for one that is larger, and quickly climb out of the smaller one and into the new one.

If you bought a pet hermit crab from a pet store, you might need to prepare these new shells. Sea snail shells are often the best choice, and they need to have enough space on the shell. A small hermit crab will need at least 3/8 inches, a medium one around 1/2 inches, and the larger one around 1 to 3 inches.

These are just a handful of the fascinating things about hermit crabs. Read below if you wish to learn more!

Land Hermit Crabs

Land Hermit Crabs
Image Credit: macular40_

Though the majority are ocean-dwellers, many different species of hermit crabs live in tropical areas of the Indo-Pacific region, the western Atlantic, and the western Caribbean. The ideal hermit crab habitat needs to have access to both land and water because they thrive close to the shore.

Despite being terrestrial, land hermit crabs return to seawater for mating and reproduction, where the female carries the eggs and then releases them into the water. When the larvae grow into adults, they then move into land.

Among the largest land hermit crab species ever found are the following:

1. Coconut Crabs (Birgus latro)

Big would be an understatement when describing coconut crabs. These enormous creatures can grow to be 40 inches (1 m) long and 10 pounds (5 kg) heavy. They can lift objects weighing as much as a 10-year-old kid, have legs that can span up to a meter, and have remarkable grip strength.

They are known to be capable of opening coconuts with the help of their enormous pincers (chelae).

The coconut crab holds the Guinness World Record for being the largest crustacean to spend its adult life on land. Additionally, it is the largest terrestrial arthropod. They are found in the Indian and Pacific Oceans to the southwest.

2. Indonesian Crab (Coenobita brevimanus)

When fully developed, Indonesian crabs can grow to be 6 to 8 inches long and 8 to 10 ounces in weight. They are ranked among the largest land hermit crabs in the Coenobita genus. These hermit crabs can be recognized by their excessively big, roundish left claws that lack stitch marks.

3. Caribbean Hermit Crab (Coenobita clypeatus)

One claw of a Caribbean crab is larger than the other, and it can reach lengths of 3 to 6 inches from front to back. When disturbed, Caribbean hermit crabs lash out with their claws, but most of the time they quietly retreat within their shell to avoid predators or when they feel threatened.

Despite their relatively large structure, Caribbean crabs are the most common species of hermit crabs and one of the two most popular crabs to have as a pet. The other one is the Ecuadorian hermit crab, which only grows to a measly 0.12 cm.

Marine Hermit Crabs

Marine Hermit Crabs
Image Credit: kensmallwood

Hermit crabs are aquatic creatures that spend the majority of their lives underwater. They inhabit saltwater habitats ranging from shallow reefs and shorelines to deep sea bottoms, hardly ever venturing onto dry land.

As compared to land hermit crabs, marine hermit crabs tend to be smaller in size. If you ever wish to take care of one, try to raise saltwater hermit crabs.

1. Giant Red Hermit Crab (Petrochirus diogenes)

As its name suggests, the largest species of the marine hermit crab is the Giant Hermit Crab, which may grow to a length of around 19 inches, including its claws. They have red coloring on their bodies, enormous claws that resemble lobsters, and bluish-stalked eyes. Its size and its strongly tubercled, red claws help to distinguish them from other hermit crabs.

2. Elegant Hermit Crab (Aniculus elegans)

The elegant hermit crab is a very common and one of the largest species of hermit crabs. Adults can grow to be 3 inches long or more. Typically, you can find them on the reef and in the debris.

They can help keep your hermit crab tanks clean as pets by eating waste and algae as they move around. Although their knuckles appear to be a different color, their legs appear to be striped. Their knuckles, which can be blue, yellow, or red, are on brown legs.

3. Dwarf Blue-Leg Hermit Crab (Clibanarius tricolor)

The Blue Leg Hermit Crab may grow to a size that allows it to fit inside a 1.5-inch shell. Any saltwater tank would benefit from having them. With their vivid blue legs, these tiny creatures will stick out in your aquarium. They scavenge fish excrement, algae, and other debris that have been dumped on the live rock and sand substrate.


Contrary to popular belief, predicting a hermit crab’s size is a lot more difficult especially because they are very dependent on their environment. As you can see, hermit crabs come in a variety of sizes as they mature. Some may end up being only a few inches long, while others may reach a peak of 40 inches.

As you’ve heard about some of the common hermit crabs and how big they may grow, this could help you in making the best decision as to what kind of hermit crab to have at home.

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