How Big are Tarantulas? Full Size Guide For Species + Tips

Mexican red-knee spider

So, how big are Tarantulas? Well, there are several different types of Tarantula out there, and there are some slight differences in their size. Also, when it comes to their age, then those same differences between the various sub-species will rear its head.

The average Tarantula can vary in size from anywhere between 4.5 inches up to 11 inches. Breeds commonly kept as pets tend to be in the 5-8 inch territory. However, there are some tarantula species out there that are smaller than 4.5 inches in size, although these are rarely kept as pets.

[Source] So, as you can already see, there will be a number of options out there for anybody interested in potentially owning a Tarantula as a pet.

So, which sub-species is going to equate to which size? Clearly, if you plan on having a pet Tarantula, it does make sense that you understand how big they are going to get when fully grown. Also, knowing how long they tend to live in captivity does help you when it comes to planning for the future.

With that in mind, let’s start exploring the various size options.

Their General Size

When we talk about their size, we are really looking at the measurement that exists from their front right leg going to their back left leg. That gives the most accurate measurement.

That’s how we have come up with the size range of anywhere between 4.5 inches to 11 inches. The problem is that there are actually over 600 different sub-species of Tarantulas out there in the world. Within those hundreds, there are some that only measure an inch or so across. In other words, they are minuscule.

Of course, having a Tarantula that’s the size of a bug is not something most people would expect. Instead, we tend to think of a Tarantula as being this big, hairy spider that is certainly very visible to the naked eye. A Tarantula the size of a bug would never create the same sense of fear as the bigger species are capable of doing.

But let’s put those small Tarantulas to one side for a second.

One of the amazing things about a Tarantula is that some sub-species can grow quite quickly. The Honduran Curly Leg species, which we mention again later, is very fast-growing.

The Tarantula is going to reach adult size from anywhere between 2 and 5 years depending on the sub-species. You must be aware of their full adult size before you go and buy a spiderling. You need to have the correct size of enclosure for your Tarantula from the outset, as they do not like to change their home, and will want to settle down in there forever.

Explaining the Size

We should make one thing clear when it comes to the size aspect. When we talk about 4.5 inches to 11 inches, we are clearly discussing the leg span and not just the body on its own.

Some species of Tarantula will have a larger leg span than others, and we can look at the Goliath bird-eating Tarantula. This guy has a body that can grow up to almost 5 inches across. However, when you add in his legs, then you get to him measuring some 11 inches across.

That makes him the largest spider in the world, and he is massive if you came across him.

But this is an interesting point about the largest spider in the world.

Scientists believe that this is about as big as they could ever possibly get. It’s all to do with their exoskeleton and their respiratory system. Thanks to the oxygen that’s in our atmosphere, they couldn’t grow any larger, as they would be unable to breathe and get enough oxygen into their body.

However, the goliath is still one big spider, but we should focus more on those species that you are most likely to go ahead and own.

When you do that, you will see that the size is nowhere near as big as the Goliath. In saying that, you are still going to own a pretty large spider. Of course, the size will then influence the enclosure you need to purchase, so let’s get into some of the more common pet species you may end up owning.

Large hairy tarantula on owner's arm

Size and Your Pet Tarantula

Of course, nobody is going to really have a Goliath as a pet Tarantula, so how about the sizes of the most common breeds that people do keep?

When you look at these kinds of stats, you quickly see that the size range is a bit narrower. It seems we like to see our Tarantula rather than having one that can easily hide away in their enclosure.

If you think of the Mexican Red-Knee, then you have a Tarantula that’s going to get to between 5 and 8 inches across in size. That in itself is pretty standard.

Then, you have the Chilean Rose. This species is going to be ever so slightly smaller in size than the Mexican Red-Knee as they come in at around 4 inches, but some may grow to in the region of 5 inches.

Then we move onto the Mexican Red Leg. The female here can live to around 30 years of age, so keep that in mind if you plan on getting one as they will be around for quite some time.

Once again, this is a popular breed to own, and their size is between 5 and 6 inches in length, so they are not that small of a spider. This breed is popular as it’s viewed as being quite docile in nature, but be warned, as they can be very easily started, and that’s when problems could arise.

But if you are new to the idea of looking after a Tarantula, then you may want to look at a breed such as the Pink Zebra Beauty. They are viewed as being perfect for those starting out as they are very docile, and the female is going to live in the region of 25 years in captivity. When it comes to their size, then it’s generally around 5.5 inches.

The point we are really making here is that the most popular breeds all have a tendency to come in around the same size, and that’s about 5 inches from leg to leg.

Something a Little Bit Bigger

If you are looking for something a little bit bigger, then a Tarantula, such as the Brazilian Black, is going to be a wonderful option. They will be in the region of 7 inches in size, so they are still not that much larger than others we have mentioned earlier on.

This species is different in that it is all black. They also seem to have a velvety style skin. With this species, the female can live for around 20 years, with the male living for around 5 years, so that’s a big difference.

Of course, if you are planning on getting a Brazilian Black, then do remember that it means a larger enclosure due to them being of a larger size.

The species we mentioned above are among the most popular sub-species of Tarantula that people tend to own as pets.

Tarantula Species Size Table Guide

Here’s a table that summarizes all the information I’ve talked about into one handy place:

SpeciesAverage Size
Goliath Bird Eating Tarantula9-11 inches
Mexican Red-Knee Spider5-8 inches
Chilean Rose4-5 inches
Pink Zebra Beauty5.5 inches
Brazilian Black7 inches

So, Our Final Thoughts

So, here are my final thoughts on the size of Tarantulas.

Sizes vary a huge amount, and that’s to be expected when you have in excess of 600 different sub-species to contend with. However, from the perspective of a pet, you can expect the female to be in the region of 5 inches in size.

There are, of course, some exceptions to this, but that is a ballpark figure.

Clearly, their size does also change the enclosure that they should be kept in, so keep size in mind when buying their home. You may also want to double check the sort of humidity they are used to in their natural environment, to allow you to then produce the same sort of conditions for your pet.

Please, do your research before you go ahead and get a pet Tarantula. Identify the sub-species you are interested in, and learn everything there is to know about how long they will live, and the size they will grow to. Even understanding how quickly they reach maturity is going to prove to be important.

After you have finish all this, it’s best to settle down for the long haul, as your pet Tarantula is going to be with you for a number of years. But with the amount of enjoyment they can bring as a pet, that’s not exactly a bad thing.

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