How Big Will My Pet Iguana Get?

If you’re considering adopting a baby iguana, you will probably encounter a tiny lizard with a long tail that looks like it will make a cute pet for your terrarium. But iguanas are among the largest lizards in the world and they grow quickly. By the time they are six months old, they might be two feet long, and when they are fully grown, they can be as big as six feet.

Sadly, many people who adopt baby iguanas don’t realize what they are in for, and they often need to be rehomed within the first year because people just don’t have space for them. So it’s a good idea to know just how big your iguana is likely to get before you take them home.

The potential size of your iguana depends on their species and also their genetics, so it is always a good idea to ask the breeder what size similar lizards they have raised have grown to. 

Below, you will find a general iguana size guide, including a detailed discussion of the potential size of the most common pet iguana species. We will also talk about what size terrarium you are likely to need to raise a healthy and happy iguana.

Iguana Growth

There are around 35 species of iguana divided into eight genera, so there is a lot of variation. This means that just saying you are adopting an iguana won’t give you much information. We need to get more specific.

Small species, such as the Fiji banded iguana and the Yucatan sprint-tailed iguana, may stay under one foot long and weigh less than half a pound when fully grown. Large species, such as the marine iguana and the Cuban rock iguana, are likely to be five feet or longer and weigh upwards of 20 pounds.

However, all baby iguanas are just three to six inches long when they hatch and weigh 0.2-0.3 pounds. But from this moment, the iguanas that are going to be big will start growing fast. Some will be born with a full set of teeth so they can start munching and growing right away. By the time they are six months old, big iguanas, such as the green iguana, could already be two feet in length.

While smaller iguana species might reach full growth at between 12 and 18 months of age, bigger iguanas can keep growing for several years. You shouldn’t expect them to be fully grown until they are three to four years old, and even then, though their growth slows, large species like the green iguana might keep growing until they are around eight years old. 

Most iguanas live between 15 and 25 years in captivity, but they can live for well over 30 years in the right conditions.

Males of all iguana species tend to be a bit larger than the females, and iguanas raised in captivity tend to be bigger than wild iguanas. This is because your pet iguana has regular access to food, a controlled environment, and minimal stress from predators to affect their growth, so they are free to grow to their full potential.

The Size Of Common Iguana Species

Below are examples of some of the most common iguana species kept as pets and how big you can expect them to grow.

Green Iguana

The green iguana is probably the most common iguana species and also one of the largest. It’s not unusual for these beautiful lizards to reach seven feet long and weigh 20 pounds or more. These are the ones that keep growing for several years, and you can expect them to reach full size between six and eight years of age.

These lizards are originally from South America, from regions of Brazil and Paraguay, where they have a herbivore-rich diet of leafy greens, fruits, veggies, and flowers. They are called green because of their stunning green color, and they also often have striking colorful markings in blue, white, black, pink, purple, and many other colors.

Below is a growth chart for a standard green iguana in captivity.

AgeWeightBody Length
Hatchling< 1 pounds6-9 inches
6 months1-1.5 pounds20-27 inches
1 year2-4 pounds28-36 inches
2 years4-5 pounds30-42 inches
3 years5-8 pounds35-48 inches
4 years10-15 pounds45-60 inches
5 years14-18 pounds50-66 inches
6 years15-20 pounds60-72 inches

Desert Iguana

The desert iguana is a popular captive species because they tend to be much smaller than your average iguana. While they can grow to anywhere from 16-24 inches, most raised as pets will get to no longer than 16 inches. They are also light, weighing just two to three ounces. This is because their tail is about 1.5 times the length of their body.

Originally from the Southwest United States and Mexico, these iguanas are known for their sandy or grayish color skin at sunrise, which will turn a warm white by midday to reflect the sun. They tend to have quite meaty arms for desert-style rock climbing, and they appreciate plenty of climbables in their habitat.

Rhinoceros Iguana

Rhinoceros iguanas are called as such because the males have a rhino-like horn. They can vary greatly in size, from as small as 24 inches to as long as 60 inches, and can weigh between 10 and 20 pounds. If you are specifically after a rhino iguana, you’ll probably be able to find a breeder that specializes in smaller pets.

Originally from Haiti and the Dominican Republic, this is another muscular species that can look quite wide. They have skin ranging from steely gray to dark green and a feisty temperament, which means that you should always be careful when handling them.

Spiny-Tailed Iguana

Quite a variety of iguanas are considered under the spiny-tailed label, and they can measure anywhere from 10 to 40 inches. But the most popular pets are the Yucatan spiny-tailed iguana, which usually reach around 10 inches in length.

Originally from central America, these lizards are named for the spines they raise in various situations. They are a pretty aggressive species, so you might see them raising them quite often. They are also fast. Speed bursts of more than 20 miles per hour have been measured. 

Iguana Tank Size

Considering how big iguanas get, you have probably guessed that they need pretty big tanks to be happy. You can approach this by starting them off in a smaller tank and growing it with them, but this can be an expensive strategy because they grow so quickly. 

There is no real problem with putting a growing iguana in a tank that is too big for them, but keeping a large iguana in a small tank will cause them stress and can adversely affect their health.

As a minimum, you should invest in a tank that is 1.5 times the length of your iguana, 1.5 times their height, and 2 times their width. But that is a minimum size; they will benefit from something larger.

Most captive adult iguanas will appreciate a tank that is at least eight feet long, six feet high, and three feet wide.

Iguana Size FAQs

Are iguanas bigger than komodo dragons?

No, komodo dragons are bigger than iguanas. While they might reach a similar length, komodo dragons are much heftier animals.

While the biggest iguanas only weigh about 30 pounds, komodo dragons can weigh as much as 100 pounds or more.

Do iguanas have predators?

In the wild, iguanas are hunted by a variety of species including hawks, owls, and snakes. But as is often the case, the biggest danger to iguanas are humans, who are destroying their natural habitats.

Are iguanas toxic?

Iguanas are non-toxic, so a bite from one of these lizards is not poisonous. They do have venom glands, but this produces a weak and harmless venom. However, they have strong jaws, so a bite can be painful and cause significant damage to the skin and flesh.

What is the lifespan of an iguana?

In captivity, most iguanas will live 10-15 years. However, they can live for much longer when kept in proper conditions. The oldest recorded iguana lived at Australia Zoo and reached 40 years and 278 days.

Adopting An Iguana

Now that you know just how much space your iguana needs, will you be taking one home? If you have the space, they make excellent companions so they are worth the investment. If you’re short on space, look at smaller species such as the desert iguana or the Yucatan spiny-tailed iguana.

Read our 10 fun facts about an iguana that you might not have known.

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