How Big Do Hermit Crabs Get? [Surprising Size Facts]


by Simon Griffiths



If you have pet hermit crabs or you planning to acquire a few hermies, it’s great knowing how big they can get in captivity.

That information will help you to monitor their growth over time. If you’re just starting size information will help you to select the right tank size.

This post goes deep into the question, how big do hermit crabs get? The post also answers other size-related questions such as

  • When does a hermie stop growing?
  • Can a small shell prevent a hermit crab from growing?
  • What hermit crab species grow the biggest?
  • What can I do to make my pet hermit crab grow bigger?

With that out of the way, let’s get into it.

How Big Do Hermit Crabs Get?
A photo showing the size of 3 species of land hermit crabs that are regularly kept as pets


How Big Do Hermit Crabs Get?

Land pet hermit crabs range between 0.5 inches and 8 inches in size. The smallest species is the Ecuadorian hermit crab, while the biggest is the Indo Hermit Crab, which can grow up to 8 inches. The Coconut crab is the largest hermit crab measuring up to 1 meter (40 inches), but very few people keep it as a pet. 

In the middle range is the Blueberry hermit crab (Coenobita purpureus) which ranges between 1-1.5 inches, while the Caribbean hermit crab (purple claw) ranges between 2 and 6 inches in size. 

Scientific namePopular name(s)Size
Coenobita clypeatusCaribbean hermit crab
Purple pincher
3 – 6 inches
4 inches on average
Coenobita compressusEcuadorian hermit crab
Pacific hermit crab
up to 12 mm (0.5 inch)
Coenobita brevimanusIndo Hermit CrabUp to 8 inches
Coenobita cavipesPassionfruit HermitUp to 4 inches
Coenobita perlatusStrawberry hermit crab3.1 inches - up to 5 inches
Coenobita purpureusJapanese Blueberry
Purple land hermit
1.1 inches to 1.5 inches
Coenobita pseudorugosusMarble hermit crab0.4 inches to 2.3 inches
Coenobita rugosusTawny Hermit Crab0.6 inches
Coenobita spinosusForest Hermit Crab
Spiked hermit crab
1.9 inches to 4.3 inches
Coenobita variabilisAustralian land hermit crab
Aussie Crab,
Crazy Crab, Calico Crab
Up to 1.6 inches
Coenobita violascensKomurasaki Land Hermit Crab
Viola Land Hermit Crab
Up to 3 inches

How Big Do Hermit Crabs Get?
A close up photo of a giant hermit coconut crab on the ground
A giant hermit crab.

The coconut crab, palm thief, or robber crab is the largest and heaviest hermit crab. However, very few people keep it as a pet. They are dangerous and have more needs than the other species.


There are over 800 species of marine and land hermit crabs. Only 17 species are terrestrial and it’s what people keep as pets. The 17 species belong to the genus Coenobita.

Every species grows differently when it comes to size and weight.

A hermit crab’s growth is dependent on how you feed it, the conditions of its tank, and its shell size. A healthy crab will molt several times a year in order to accommodate its growth.

If your crab is living in a small shell and there is no bigger shell to vacate to, then there is a chance that your crab won’t grow big. In fact, some experts say that these creatures have the ability to grow smaller.

Related read what to do if your hermit crab leaves its shell 

Hermit crabs are grouped into 7 sizes

  • Micro – 0.5 inches and below
  • X-Small – up to 1 inch
  • Small – 1 to 2 inches
  • Medium – up to 2.5 inches
  • Large – 3 inches
  • X-large – 3.5 to 4 inches
  • Jumbo – 4 – 10 inches
  • Giant – Over 10 inches

Hermit tips:

  • All crabs belong to the phylum Arthropoda
  • Terrestrial hermit crabs and coconut crabs make up the family Coenobitidae.
  • The coconut crab is the largest terrestrial arthropod. Larger than any terrestrial insects, spiders, scorpions and millipedes, and centipedes.

Hermit Crab Sizes – Popular Species

There are so many hermit crab species, but we can’t cover all of them. We are just going to highlight the most common species that you are likely to find in the pet store.

1. Caribbean/ Purple Pinchers Hermit Crab (Coenobita clypeatus )

Also known as, soldier crab, tree crab, or West Atlantic crab

Purple Pincher Hermit Crab is the most common pet hermit crab species and can live for up to 20 years in captivity. PPs are social animals and rarely do well in isolation. Purple Pinchers or Caribbean hermit crabs attain 2-5 inches in captivity. However, they can grow to jumbo size if you take care of them and provide them with enough space and bigger shells.

However, Jumbo hermit crabs are difficult to care for making them ideal for experienced hermit crab lovers.

2. Ecuadorian hermit crab (Coenobita compressus)

If you are looking for small hermit crab species, then I would suggest you go for the Ecuadorian. They are quite common in pet stores and the shores as well.  Being one of the smallest species, Ecuadorian hermit crabs can only grow up to 0.5 inches in length (12mm).

3. Strawberry hermit crab (Coenobita perlatus)

As the name suggests, these hermit crabs resemble strawberries because of their red color. Strawberry hermit crabs can grow up to 6 inches in their natural habitat. However, they will rarely get past 5 inches in captivity.

4. Okinawan Blueberry Hermit Crab (Coenobita purpureus)

Blueberry crabs are not that common, but they are quite sought after by crabbers. They are mostly found in japan and they have a bluish color. In terms of size, Blueberry Hermit Crabs can grow up to 18mm.

5. Indonesian Hermit Crab (Coenobita brevimanus)

Also called Short-sheared land hermit crab, an Indo Hermit Crab is a big hermit crab. Coenobita brevimanus can grow up to 8 inches. This makes a great option for those looking specifically for a big hermit crab

A large Indo hermit crab.

6. Coconut Crab/Palm Thief/(Birgus latro)

Coconut Crab is the largest hermit crab in the world. These giant crabs are so large and powerful that they can crack open a coconut. These crabs can get up to 1 meter in length, weighing 4.5 kg. Since they can get dangerous when provoked, very few people keep them as pets. Also, they require a huge crabitat to survive.

Does A Hermit Crab’s Size Determine the Size of the Cage

Yes, the crab’s size should influence the crabitat you should invest in. There is no way a large hermit crab can survive in a small tank. A large crab will need to have enough substrate to dig into and enough space to play.

On the other hand, small crabs can do well in small enclosures. You can as well get a medium-sized tank to house two or three small hermit crabs.

Whichever tank you get, make sure that the hermit crabs are not living in cramped conditions. They should have enough room to climb, dig, play, hide and do their thing.

Below is a table that shows the recommended tank size depending on how big your hermit crab is.

Size of CrabRecommended Tank SizeSpace For Each Hermit CrabMinimum Substrate Depth
Micro5 gallon0.65 gallon3 inches
Teeny5 gallon1 gallon4 inches
Small10 gallon2.5 gallons5 inches
Medium10 gallon4 gallons6.5 inches
Large20 gallon5.5 gallons8 inches
Extra Large30 gallon6.5 gallons10 inches
Jumbo50 gallon15 gallons12 inches

Frequently Asked Questions on Hermit Crab Sizes

How big is a 10-year-old hermit crab?

The size will depend on the species of the hermit crab. For instance, an Indo Hermit Crab (Coenobita brevimanus) can grow up to 8 inches making it one of the largest terrestrial hermit crabs. On the other hand, a Caribbean hermit crab/Purple pincher (Coenobita clypeatus) can grow up to 6 inches.

How big is the world’s biggest hermit crab?

The world’s biggest hermit crab is the Coconut Crab (Birgus latro). It’s also the largest land-living arthropod. The coconut crab or the Palm Thief can grow up to 1 meter (3.2 feet) weighing up to 4.5 kg.

Fun Fact
A coconut crab is called a robber crab because of carrying with it anything it comes across such as pots, silverware, and coconut shells.

What is the biggest hermit crab ever recorded?

The world’s biggest crab is the Coconut Crab also known as the Palm Thief or Robber Crab. The coconut crab has a Guinness World Record for the heaviest crustacean on land and the biggest crab ever.

How big can hermit crabs get

How big can a hermit crab get depends on the species. The Indo hermie can get up to 10 inches while the Purple pincher ranges between 4 and 6 inches making it the second biggest pet hermit crab.

How big is a jumbo hermit crab?

A jumbo hermit crab is any hermit that is 4 inches and above. Most hermit crabs do not grow past 4 inches in captivity. There are, however, some crabs that get up to 8 inches even in Captivity such as the Indo Hermit Crab.

Do hermit crabs ever stop growing

No, hermit crabs do not stop growing. This is because they never stop molting. However, old hermit crabs take longer before molting.

The 17 species of terrestrial hermit crabs

Scientific namePopular nameNative
Coenobita clypeatusCaribbean hermit crab

Soldier crab

West Atlantic crab

Tree crab

Purple pincher
West Atlantic, Belize

Southern Florida


West Indies
Coenobita compressusEcuadorian hermit crab

Pacific hermit crab
Mexico to Chile
Coenobita brevimanusIndo Hermit CrabIndonesia east coast of Africa
South west Pacific Ocean.
Coenobita cavipesPassionfruit HermitEast Africa Indonesia, Philippines, China
Coenobita perlatusStrawberry hermit crabIndo-Pacific
Coenobita purpureusJapanese Blueberry Hermit Crab

Okinawan blueberry hermit crab

Purple land hermit crab

Ryukyuan Blueberry
Coenobita pseudorugosusMarble hermit crabPhilippines and Southwest Madagascar
Coenobita rugosusTawny Hermit CrabIndonesia, Australia and the east African coast
Coenobita spinosusForest Hermit Crab

Spiked hermit crab
Polynesian islands,
northern coast of Australia
Coenobita variabilisAustralian land hermit crab

Aussie Crab,
Crazy Crab, Calico Crab
Coenobita violascensKomurasaki Land Hermit Crab

Viola Land Hermit Crab
Indonesia, Nicobar Islands, Thailand, Cambodia, Philippines, and Tanzania
Coenobita lilaLila hermit crabSingapore
Birgus latroRobber crab or Palm thief.southwest Pacific and Indian oceans
Coenobita scaevolaNAwestern Indian Ocean and Red Sea
Coenobita rubescensNAAtlantic coast of western Africa
Coenobita olivieriNANA
Coenobita longitarsisNANA
Coenobita carnescensNANA

Wrapping Up

That pretty much sums it up for the question – how big do hermit crabs get? We’ve seen that hermit crabs can grow up to 6 or even 8 inches if they are well taken care of. However, most pet hermit crabs will rarely hit the 6 inches mark when in captivity. On average, most pet hermit crabs range from 1.5 to 4 inches in size. Large hermit crabs include the Indo hermit crab, Caribbean/Purple pincher, Passionfruit Hermit, Strawberry hermit crab, and Forest Hermit Crab.

References list




Simon Griffiths

Hi guys, my name is Simon, a fellow pet lover. I love everything about traditional and exotic pets so I am here to help you create a better home for your pets.