How Big Do Turtles Grow? (+Growth Charts)

Most turtles start out as small and adorable little creatures, but as we all know, they won’t stay that small forever. But for how long will they stay that way? How big will they get?

On average a turtle can range in size anywhere from 3 to 10 inches. The average size of a turtle is influenced by factors like diet, habitat, gender, genetics, and most importantly species.

For their first few years, most turtles will stay small, rarely getting bigger than 4 inches. But soon after some of them will start to grow bigger. How big will they get is influenced mostly by their habitat and diet, but the most important factor is their species, so let’s start by taking a look at that.

Growth Charts for Different Turtle Species

In order to keep the article slightly shorter, and make it easier to navigate, I’ve chosen only some of the most popular pet turtle species, but if you are interested in a species that is not on this list, you can leave a comment at the end of the article and I will gladly add it.

How Big Do Red-Eared Sliders Grow? (+ Growth Chart)

Red-eared sliders are definitely the most popular pet turtles, and one of the reasons for this is that people get them when they are still babies, and most of them are no bigger than 1 inch (2.5 cm). But most people will find out soon enough that they won’t stay that small for long.

During their first year, red-eared sliders tend to double or triple in size reaching a size between 2 and inches (5 and 7.5 cm).

After that, the growth continues at an accelerated rate, for the next two years, as most red-eared sliders continue to grow as much as 2 inches per year. By the age of 3, most red-eared sliders have a size of 7 inches. At this point, the growth slows down to about 1 inch per year, and it continues that way until the turtle reaches the age of 5.

After the age of 5, the growth slows down, as most turtles grow less than half an inch per year. And they will continue to grow at this rate up until they reach the size between 8 and 12 inches, which is their maximum size.

After this point, very few red-eared sliders continue to grow any further, and if they do, they do it at a very slow pace, which is bearly noticeable.

Age	Average Size (Inches)	Average Size (Centimeters)
1	3	8
2	5	13
3	7	18
4	8	20
5	9	23
8	10	25

Before we move to the next species I want to remind you that those are just the averages and that there are a lot of factors that contribute to the growth rate, so those numbers won’t apply to all turtles.

How Big Do Painted Turtles Grow? (+ Growth Chart)

Compared to red-eared sliders, painted turtles are much smaller, only reaching sizes of around 6 inches (15 cm). And as a result, their growth rate is also slower. But unlike red-eared sliders who reach their maximum size around the age of 8, painted turtles continue to grow, until they reach the age of 20.

Like most turtles, painted turtles start life with a size of about 1 inch (2.5 cm). And during their first tear, they will reach a size of about 2 inches (5 cm).

For the next two years, up until the age of 3, they will grow at a rate of 1 inch (2.5 cm), per year. After that, the growth rate will go down a lot.

Most painted turtles reach a size of 4 inches (9 cm) at the age of 3. But during the next 7 years, most of them will only grow one more inch, reaching the size of 5 inches.

Most painted turtles reach their maximum size, of 6 inches (15 cm) when they are 20 years old.

Age	Average Size (Inches)	Average Size (Centimeters)
1	2	5
2	3	7
3	4	9
10	5	12
20	6	15

How Big Do Box Turtles Grow? (+ Growth Chart)

Box turtles are also a smaller species, reaching a maximum size of 6 inches (15 cm). But comparative to painted turtles, they reach their maximum size much faster.

During their first year, most box turtles will reach an average size of 2 inches, after which they will grow about 1 inch per year, up until they reach the size of 4 inches (9 cm). And this is the point when the growth slows down.

After the age of 3 years, the growth will slow down to about 0.4 inches per year (1 cm), up until they reach a size of about 6 inches (15 cm), at which point the growth stops.

Age	Average Size (Inches)	Average Size (Centimeters)
1	2	5
2	3	7
3	4	9
8	6	15

What Makes Turtles Grow

Food

A poorly fed turtle won’t grow as big as a turtle with a good diet.

We all know that the growth of every living being is influenced by what they eat, but due to the unique anatomy of the turtle, they are affected by this more than any other animal.

Turtles need two things from their food in order to grow, proteins and calcium.

A turtle that doesn’t get enough proteins or calcium will grow at a much slower rate or stop growing completely until they manage to get enough. This can be clearly seen by comparing pet turtles with wild turtles that are about the same age.

In the wild turtles don’t always find what to eat, and what they manage to find doesn’t always contain enough nutrients. While a pet turtle will usually have a balanced diet that contains everything that they need.

To give you an example of how drastic the differences can be. There have been studies that looked at red-eared sliders that were born at around the same time, but lived that lived in different environments:

The red-eared slider that lived in captivity had a size of 10 inches (25 cm) when it was 5 years old.
The one that lived in the wild, in an area with lots of food sources, reached a size of 8 inches (20 cm) when it was 5 years.
And the one that lived in an area with few food sources reached a size of just 6 inches (15 cm).

As you can see the availability, and quality of the food can have a very big impact. But food is not the only thing that affects the growth rate, there are a few more things that can make a big difference.

UVB Rays

Both wild and pet turtles bask, wild turtles do it in the sun, while pet turtles do it in the basking area. When turtles bask they do two things, the first one is that they heat up their bodies (as turtles can’t produce their own body heat), and secondly, they absorb UVB rays which help them process the calcium in their body.

Without UVB rays all the calcium that they eat won’t be properly processed and won’t be able to help them grow.

In the wild conditions aren’t always ideal, so most turtles don’t get as many UVB rays as they would need to properly process the calcium that they get from food, and this can slow down their growth.

On the other hand, pet turtles will always have a basking area that is perfect for basking, so they will never lack UVB rays.

Gender

In the case of a lot of turtle species, females tend to grow bigger and faster than males, and those differences are very noticeable. And in some turtle species, the exact opposite is true, males grow bigger and faster.

For example, female map turtles can reach a maximum size of around 11 inches (28 cm), while most makes reach a size of around 6 inches (15 cm).

Some differences in size between genders are present in most turtle species, but they are not always as significant as this one.

If you want to find out what gender your turtle is, to know how big it can grow, you should check out this article: How to Tell If Your Turtle Is Male or Female (with Pictures), where I cover the subject more in-depth.

Hibernation

One often overlooked, but very important thing regarding growth rates is hibernation,

Wild turtles need to hibernate 3 months per year, during which they won’t grow at all, while pet turtles don’t need to hibernate.

This basically means that pet turtles have 12 months at their disposal to grow, every year, while wild turtles only 9.

During hibernation turtles can’t get any food, so they have to use all the energy and nutrients that they have to keep vital functions alive, so they can’t grow at all during this period. But pet turtles don’t have to do this.

Genetics

And of course, a very important part is played by genetics. Some turtles are simply unable to grow as big as others, and some turtles will grow faster than other turtles, even if they are from the same species.

Final Thoughts

Most turtles will grow about 1 inch per year for the first years of their life, then the growth will start to slow down. How much it slows down depends on the species.

But no two turtles will grow at the same rate, some will grow faster, some will grow slower, some will grow for just 8 years, while others will continue to grow for 20.

But as important as the species of the turtle is, to turtle can grow properly without a proper diet or access to UVB light, so in order to ensure that your turtle can have a healty growth rate make sure that you are feeding it correctly and that the basking area is in order.

I hope this article answered all of your questions, but in case there is something else that you would like to know, that I haven’t covered in the article, feel free to leave a comment in the section below, and I will answer it as soon as possible.