How Big Do Red-Eared Sliders Get? Size & Growth Chart

Red-eared sliders are often sold as small juveniles in many pet stores around the world.

Though they start out at just 1 inch long as hatchlings, sliders grow much larger than most people think.

Before buying one, owners should know how big their turtle could get. They grow very fast in their first three years and soon outgrow small enclosures.

Want to find out how big do red-eared slider turtles get, and how fast can they grow?

Continue reading for red-eared slider size and growth charts and factors that influence their growth rate.

How Big Do Red-Eared Sliders Get?

How Big Do Red-Eared Sliders Get

Full grown red-eared slider size varies based on gender, nutrition, health and genetics.

These aquatic reptiles can grow surprisingly large under the right conditions, though there is always some variation between individuals.

Most adult red-eared sliders measure between 5 and 11 inches.

The average size for males is between 5 and 9 inches, while the average size for females is between 8 and 11 inches. In rare cases, some large females can reach over 11 inches!

They are larger than other pet species like Painted Turtles who measure 4-10 inches.

Males and females have different full grown lengths as adults.

It is important to be aware that average lengths and weights will not be 100% accurate for every turtle.

Healthy sliders may fall below 5 inches or above 11 inches, depending on their environment, diet and parents. Due to this natural variation and overlap in male and female red-eared slider sizes, a small female may not grow as large as a big male.

Their large shell is one of the reasons why this turtle species is so successful in the wild.

If they survive to adulthood (when they are 5 to 6 years old and 4 to 7 inches long), red-eared sliders have few natural predators. Of course, pet turtles do not need to worry about predators.

To thrive as pets, they require a large tank where they are able to swim, climb, and show their natural behaviors. They also need a healthy diet to properly fuel their growth.

When fully grown pet red-eared sliders need a 100-gallon aquarium with plenty of clean water.

As a rule, the water should be twice as deep as your slider is long. If you have a 5-inch-long turtle, the water in its tank should be at least 10 inches deep.

It is best to assume that your red-eared slider will grow to a larger than average size. Even if your turtle turns out to be small, allowing extra room in a tank is better than purchasing a tank that is cramped.

Baby

Baby red-eared sliders are tiny at hatching, only 0.9–1.3 inches in length!

At this age they weigh just over 2 ounces.

Male and female hatchlings are the same size and look very similar. Until they reach 2-6 years old, you may not be able to tell the gender of your slider.

Hatchling sliders grow quickly and don’t stay small for long. Within a few months, they will put on another inch to their total shell diameter. By the time they are 2 years old, baby sliders will be 3 inches long and weigh 1 to 2 pounds.

Their rapid growth rate helps them survive in the wild.

As hatchlings their shells are so small that they don’t offer much protection against snakes, birds, foxes, and other hungry animals.

Beginner keepers are unlikely to adopt baby red-eared sliders under five years old. This is because it is illegal to sell baby turtles under 4 inches long in the United States. Turtles are common carriers of salmonella, and the small size of hatchlings makes it easier for young children to handle them and become sick.

Juvenile

Red-eared sliders become juveniles once they reach 1 year old.

At this point, most males and females are usually 1.5 to 2.5 inches and 0.9 to 1.5 pounds.

Young juveniles have a very high metabolic rate. It is at this age that they go through their fastest growth period as they develop from a baby to an adult. They can add increase their total length by 50% to 75% every year. Because of their fast growth, diet is very important for juveniles.

If your slider is 2 inches long at 1 year old, it can grow to be 3 to 3.5 inches when it turns 2 years old.

The size range for juveniles varies quite a bit.

Young juveniles (yearlings) are typically 1.5 to 2 inches long and weigh 0.92 to 1.53 pounds.

More mature juveniles around 4 years are between 3 and 5 inches and 1.84 to 3 pounds.

Sliders are considered juveniles until they reach 5 years old. At around 5 years old they reach adulthood which is when males and females will likely be different lengths.

Adult

An adult slider will measure anywhere from 5 to 11 inches long.

Gender is the greatest deciding factor in red-eared slider size.

Even when cared for properly, male sliders are not as large as females. A male given the same diet, enclosure and husbandry will likely be smaller than a female.

Female sliders are heavier, longer, and overall larger.

The reason why males are smaller is not well understood. Females may have evolved to grow larger to help them store more energy to develop and lay eggs.

The difference between males and females becomes noticeable when they reach around 5 years old.

Male vs female full grown Red-Eared Slider Size

How Big Do Male Red-Eared Sliders Get?

Adult male red-eared sliders grow between 5 and 7 inches and can weigh 2 to 3 pounds, depending on shell length.

How Big Do Female Red-Eared Sliders Get?

Female red-eared sliders average 9-11 inches, but a large female can measure up to 11.5 inches long and weigh up to 7 pounds if given enough space. Large enclosures are especially important for females because they grow much larger.

Wild Size

The growth of a red-eared slider depends on many factors.

There is no guarantee that a pet slider will always be bigger than a wild one.

Pet turtles that are well-cared-for and given a healthy diet are likely to grow larger than wild turtles who live in a harsh environment. A pet kept in a dirty, cramped tank and fed a poor diet is not likely to grow as large as a healthy turtle in the wild.

A wild, adult red-eared slider can reach 5 to 11 inches.

Fully-grown females in the wild may reach 8 to 11 inches, while males reach 5 to 7 inches.

Most wild turtles do not live long enough to reach adulthood. The chances of being killed by a predator are greatest when they are small.

Red-Eared Slider Max Size

Red-Eared Slider Size

The current record for a red-eared slider comes from Minnesota, where a man found a turtle measuring 11.625 inches! The previous record-holder was a slider found in Kansas that measured 11.375 inches.

With a perfect combination of diet, warm weather, tank setup, genetics and luck, red-eared sliders can grow larger than 11 inches.

There are unconfirmed reports of pet sliders growing to 12 inches, though these haven’t been verified.

Unfortunately, red-eared sliders have been found outside of their native range in many parts of the world. These sliders were likely released by owners who were not prepared to care for an 11-inch pet turtle.

To be a responsible owner, you should be prepared and ready for the possibility that your turtle will grow to 11 inches.

How Quickly Do Red-Eared Sliders Grow?

Red-eared sliders do not grow at the same rate for their entire lives.

Sliders grow faster when they are young. As they age, their growth rate gradually slows:

Age Growth Rate/year
Hatchlings (0-2 years) 1.5 inches
Juveniles (2-5 years) 1 inch
Adult (5-7 years) 0.5 – 1 inch
Senior (8+ years) <0.2 inches

Hatchlings are about 1 inch long and grow at around 1.5 inches per year for the first 2 years.

After this initial growth spurt, their growth slows down to 1 inch per year for the next 3 years.

Red-eared slider growth rates tend to be around 1 inch per year until they reach around 5 years old.

This rapid growth is very helpful for hatchlings, who are at a high risk of being eaten by predators when they are small. Faster growth when they are young means that they will gain size (and protection from predators) quickly.

At 6 years old their growth slows to just a centimeter or two each year.

They will grow at this slower rate until they reach around 8 years old.

Their growth rate decreases as they age, but these reptiles never truly stop growing.

From adulthood until the end of its life, a red-eared slider may grow an additional inch or two. This extra growth is so slow that most turtle owners do not even notice it. They will not put on as much size as they did as a hatchling or juvenile.

The change in an aquatic turtle’s growth rate from juvenile to adult happens at the same time as a change in their diet. Young sliders eat more protein than adults so they can grow faster.

As they age, they need less protein because they grow more slowly.

This diet change is also true of other reptiles like bearded dragons.

Size Chart By Age

Every slider is unique and will grow at a slightly different rate. However, it is likely that the size of your red-eared slider will fall within the average range below. The averages below are based on measurements from hundreds of pet and wild individuals.

Red-Eared Slider Size Chart
Age Male Female Description
0 – 6 months 0.9 – 1.1 inches 0.9 – 1.1 inches Hatchlings will add several millimeters to their shell length each month.
6 – 10 months 1 – 1.5 inches 1 – 1.5 inches This stage is when they grow the quickest.
1 year 1.5 – 2.5 inches 1.5 – 2.5 inches Yearlings will continue to grow, though not quite as fast as they did as hatchlings.
2 years 2 – 3 inches 2 – 3 inches Juveniles begin developing secondary gender characteristics like long claws and a concave shell.
3 years 3 – 3.5 inches 3 – 4 inches The growth of males and females starts to slow.
4 years 4 – 4.5 inches 4 – 5 inches They are almost adults and their growth rate continues to gradually slow.
5 – 6 years 4 – 5 inches 5.5 – 7 inches The size difference between males and females starts to become obvious now.
6 – 8 years 5 – 6 inches 7 – 10 inches They are considered full grown adults and are close to their final length.
8+ years 5 – 7 inches 8 – 11 inches They will continue to grow slowly for the rest of their lives, but won’t put on significant shell length.

You can calculate the full grown size of a red-eared slider by simply dividing its length by its age.

If you know your turtle’s age, you can predict how big it will be using the growth chart above.

Knowing how big do red-eared sliders get will help you prepare, plan, and know what to expect.

When Are They Fully Grown?

It is important to know when your red-eared slider is fully grown.

Sliders are usually fully grown when they reach 7 to 8 years old; 9 years is considered the upper limit.

Some sliders mature quicker than others and may reach their adult size at 7 years old. However, it takes most 7 to 8 years to reach their full grown length.

Once your turtle hits age 9, you can be sure that it is fully grown.

Full grown male red-eared sliders are 5 to 7 inches long and 1 to 3 pounds, while females are 8 to 11 inches long and up to 7 pounds. Sliders are not fully grown until they reach this size.

It is important to note that slider turtles are not fully grown when they become sexually mature (around ages 5 or 6). They still have plenty of growing to do and females can go from 6 to 11 inches during this time.

Reasons Why They Might Not Grow Properly

Red-eared sliders
The number one reason for a red-eared slider not growing is a bad diet.

Nutrition is important to building bone, muscle, shell and skin.

A turtle without the right food will not grow properly, even if all other parts of their care are excellent.

Red-eared slider turtles grow quickly during their first two years of life. They need a healthy, protein-heavy diet to properly grow. Juveniles need high-protein foods to fuel their growth; those who are not given enough protein grow much more slowly.

Vitamins and minerals are also essential for healthy growth.

Slider turtles should be fed a variety of fresh vegetables, invertebrates, leafy greens and turtle food.

Cool temperatures, a small enclosure, lack of proper lighting, and dirty conditions can also cause a red-eared slider to grow slowly.

  • Tank Size

A common myth is that turtles will only grow as big as their tank.

Keeping a slider in cramped conditions will not stop them from growing big. Instead it will prevent them from exercising, which increases the risk of health problems, shell deformities and disease.

Red-eared sliders should have plenty of room to move around.

Owners who buy baby turtles should be prepared to upgrade their tank setup from 30-gallons. A 100-gallon tank is perfect for an adult.

Turtles kept in large spacious tanks are overall healthier and faster-growing.

  • Tank Setup

You can increase the growth rate of a red-eared slider by giving them a stress-free environment.

Sliders that are stressed by inadequate tank setups tend to have stunted growth compared to those that are happy and relaxed.

Make sure your tank is fitted with a high-powered UV bulb over the basking/dry dock area. UVB and UVA light helps them to properly develop bones and shell.

  • Tank Temperature

Red-eared sliders depend on the temperature of their environment to thrive.

In cool temperatures, their energy levels decrease and they are not able to digest their food properly.

This means in colder environments they do not grow as fast as they would in a warm environment.

At A Glance

Baby sliders can double their shell diameter within their first year, growing from 1 inch to 2 inches.

The growth rate of a slider is naturally fastest when they are juveniles.

Red-eared sliders are often sold as juveniles when they are around 4 inches in size.

Most full grown red-eared sliders measure between 5 and 11 inches long.

The average red-eared slider size for adult males is between 5 and 9 inches, while females are larger between 8 and 11 inches.

Once your turtle hits age 9, you can be sure that it is fully grown. Their growth slows down enough after 9 years old, that they don’t get noticeably bigger.

Temperature, diet, tank setup, and genetics all determine how fast a red-eared slider will grow. Those with a spacious enclosure and a nutritious diet are more likely to grow larger.

Did you learn something new about these impressive turtles? Let us know in the comments.

About Nigel Robert

Nigel Robert Nigel is the managing editor at More Reptiles. He is a lifelong reptile lover, biologist and wildlife consultant who brings a decade of experience working in reptile conservation and consultancy. He joined our team in 2020 and when he’s not reviewing reptile care sheets, he’s out looking for reptiles in the wild!

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