How Big Do Brazilian Rainbow Boas Get?

The Brazilian rainbow boa (Epicrates cenchria) is a lovely snake with an iridescent pattern to its scales. These snakes are growing in popularity as pets thanks to their beautiful appearance.

You may be wondering how big do Brazilian rainbow boas get.

On average, Brazilian rainbow boas are 4 to 6 feet in length as adults. Females are typically larger than males. Some females have been known to grow to 7 feet in length. Newborns are typically 15-20 inches at birth.

Sexual Dimorphism

Like many snakes, the Brazilian rainbow boa is sexually dimorphic. Females grow to be much longer than the males typically. This is one of the few visual signs of sex in these snakes.

However, it isnā€™t a perfect indicator since there is significant overlap in the size ranges. Males will stick around 4-5 feet while females are typically in the upper range of 5-6 feet.

Size at Birth

Everything you need to know about caring for Brazilian Rainbow Boas in captivity:
Read our Brazilian Rainbow Boa Care Sheet (Complete Guide)

Rainbow boas are interesting because these snakes are oviviparous. This means that they give birth to live young rather than lay eggs.

Females will give birth to 12 to 25 babies in one litter. The babies will be born in a small, clear sac that they will break out of. Females will also produce slugs or unfertilized egg sacs that never fully developed.

Most babies will be between 15 and 20 inches at birth. These snakes grow very rapidly after this point.Ā 

1 Year

young brazilian rainbow boa

At 1 year of age, most snakes will be between 36 and 40 inches long, basically doubled in length.

These snakes will look very slim at this stage, since putting on weight is something snakes do as they reach sexual maturity. A yearling rainbow boa will eat anything it can to fuel its growth.

The next few years will be dedicated to reaching its adult length and weight.

Sexual Maturity

Size is more important for sexual maturity than age for snakes. Many rainbow boas will be 4 to 5 years old before they can breed. Some breeders will also wait si the snakeā€™s can put on weight.

Males will typically refuse to eat during the breeding season. Females will not eat regularly once they are gravid. The babies take up a lot of space so the female wonā€™t be able to eat her typical meals.

Females also lose muscle mass, which can make it difficult for her to hunt and subdue prey.

Rainbow boas rely on constriction to kill prey, so losing muscle mass means that they canā€™t kill prey. Most breeders will offer much smaller meals in the hopes the female will eat and keep her strength up.

Females are typically considered to be sexually mature at 4.5 feet long and about 4 years old. Males are slightly shorter at about 3.5 feet.

A breeding female should weigh around 1,500 grams or she may be too small for a successful litter. Snakes put a lot of energy into reproducing, so it can be fatal if they are already thin or stressed before you breed them.

Further Growth

woman handling a rainbow boa

Brazilian rainbow boas will keep growing after sexual maturity. A female snake can reach 6-7 feet if she is on the large size. One interesting thing to note is that adult snakes keep growing.

Snakes do not have determinate growth like humans do. Your rainbow boa will continue to grow throughout the 20-30 years they can live in captivity.

Thankfully, the growth rate slows immensely so you donā€™t need to worry about having a massive snake you need to house. The only way you will notice a real difference in the size of your pet is if you keep very good records of the growth of your snake.

You may notice that it has gotten longer if you compare measurements taken years apart with an adult.

The biggest noticeable difference with adult snakes is they are typically thicker and heavier than a younger snake. Most older snakes feel very solid compared to sub-adults.

This only changes in elderly snakes. Many species of snakes will show reduced muscle mass and tone right before they pass of old age.


rainbow boa's head

Newborn Brazilian rainbow boas are typically only 15 to 30 grams at birth. They will shoot up and put on weight rapidly as they age. A large female may be up to 4,000 grams as an adult snake.

Anything more may indicate that you snake is obese. These snakes are very voracious and will eat as often as you offer food for the most part. This means they can be prone to obesity.

Keep weighing your snake and learn what a healthy snake looks like. An adult should stay fairly stable in weight. Any major changes mean that your feeding schedule is off.

Make sure you feed rodents that are noi wider than the thickest part of your snake. If you keep up on weighing your snake, you can feed prey that is between 10 and 15% of your snakeā€™s weight.

Offer adults food every 10 days or what is needed to maintain the snakeā€™s weight. If you intend to breed your snakes, make sure you offer more frequent meals so they have enough energy to breed.Ā 


Brazilian rainbow boas are a bit longer than many other common pet snakes, but they are fairly similar in weight. They do need more space, but they can be great pets.

If you have any questions or comments, please leave them below.

1 thought on ā€œHow Big Do Brazilian Rainbow Boas Get?ā€

  1. Do they grow large enough for jumbo rats and will it weight bout same as adult ball python which can exceed 4500 grams


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