How to Tell the Age of a Turtle (Beginners Guide + Pictures)

Your turtle’s age may be a mystery to you if your new friend was adopted or rescued. Finding the age of a turtle is not an easy task, but there are a lot of methods that you can use to make an educated guess.

The best way to tell the age of a turtle is to count the growth rings (annuli) on its shell and divide them by 2. Those rings form while the turtle is growing and are one of the best indicators of a turtle’s age.

This method, while not perfect is extremely easy to use and can give you a good approximation of the age of your turtle. But this is not the only method that you can use, and to get the best results you should combine it with other methods. Now let’s take a look at what are the best ways to tell the age of a turtle.

Counting the Rings Method

This is a very simple and quite accurate method that can be used by anybody to guess the age of their turtle.

The rings that you can count are present on the shell of most turtles. Here are a few pictures.

After you are done counting the rings, just divide that number by 2 and you’ve got the age of your turtle. It’s that simple.

But as you can imagine this method is not 100% perfect, and the reason for this is that at one point the turtle will stop growing and the new rings will be harder to spot.

The rings are formed as the turtle grows. And since turtles don’t grow at the same rate all year round, this will create some visual signs, in this case, the rings.

After a certain age turtles will slow down their growth considerably, and at this point the new rings will be harder to spot, so it will be easier to make errors when counting them.

But telling the exact age of a turtle is extremely hard, and this method does a pretty good job. Even if it doesn’t work too well on old turtles, you should still get a pretty good estimate, and in the case of younger turtles, you should be able to get an exact age.

But as good as this method is, there are other methods that can be just as good if not even better, so let’s take a look at them as well.

The Size Method

This is another very simple yet effective method, but unlike the previous method, it requires some knowledge about the species of the turtle, which I will provide.

So to put this method into practice you simply have to measure the shell of your turtle and compare it to a table.

Here are 3 tables, one for Red-Eared Sliders, one for Painted Turtles, and one for Box Turtles.

Red-Eared Sliders

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

Painted Turtles

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

Box Turtles

Box turtles are also a smaller species, reaching a maximum size of 6 inches (15 cm). But compared 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

But as you can see this method has its limitations. The first one is that once the turtle reaches its maximum size you can’t really use this method anymore.

The second one is that turtles can have their growth stopped by external factors like lack of food, long winters, etc.

So, while this method is great if you want to find out the age of a young turtle, it’s not so useful when it comes to older turtles. But it can at least give you an idea of the minimum age.

One more problem with this method is that depending on the species of the turtle, sometimes females can be significantly larger than males, but in order to find out if a turtle is male or female you will have to wait for them to reach maturity, since that is when the visual signs appear, but by that point, the turtle has almost reached its maximum size.

If you want to know how to find out if your turtle is male or female you should check out this article: How to Tell If Your Turtle Is Male or Female (with Pictures).

Dietary Preferences

Most turtles are omnivorous, meaning that they can eat both plant matter (fruits, vegetables, etc) and meat. But as their age changes, so do their dietary preferences.

Younger turtles that are still growing will always prefer meat over anything else. This is because meat contains a lot of protein, which is what turtles need in order to grow.

On the other hand, older turtles, who stopped growing, are not as thrilled about meat anymore. They will still eat it if you put it in front of them, but if they have to choose between chasing a fish or eating a plant that is in front of them, they will go for the plant.

Visual Cues

Visual cues can tell you a lot about the turtle’s age.

One of the first differences that you will notice between a younger and an older turtle is their speed. Older turtles tend to move significantly slower than a younger turtle.

Another difference is in the shell, the older a turtle is, the more worn out the shell will look, due to scratches and daily wear and tear.

Left side young Red-Eared Slider, Right side old Red-Eared Slider

Another visual difference comes from the colors of the shell. Most turtles start their life with very bright and intense colors, and as they age those colors will continue to fade. Even after the turtle has reached its maximum size, the colors will continue to fade out.

Studying the Skeleton

Out of all the methods on the list, this is the most accurate, unfortunately, it’s very complex and can’t be used on turtles that are still alive.

When using this method scientists look at the LAGs (lines of arrested annual growth) of skeletal tissues to determine the age and growth rate of a turtle. The humerus, scapula, ilium, and femur are the bones that are usually studied.

This method has a very high degree of accuracy and is usually used to determine the age and growth rates of sea turtles, but it can also be used for other types of turtles, like red-eared soldiers, snapping turtles, tortoises, etc.

Mark-Recapture

This method is mainly used by biologists to determine the age of a turtle, and unlike the previous one, it is used on live turtles.

When using this method turtle biologists will use a file or a small drill to carefully place a mark on the shell of a wild caught turtle. Those marks are usually small, so the turtle won’t be affected by them, but noticeable to make sure that the measurements will be accurate.

After the mark is placed the turtle will be released in the wild form where it came. After a period of time, these turtles will be caught back and their shells will be studied to see their evolution and how the mark age compares to the ring counting method. After that turtles are free once again to go back in the wild.

Studies that use this method are usually long-term and can help determine the age a turtle can reach. For example, one study that used this method was conducted on multiple turtles that belonged to the following species: slider turtles, eastern mud turtles, and painted turtles. When they were first caught the turtles were estimated to be between 6 and 10 years old. The next part of the study took place 25 years later. A lot of the turtles were found, and this proved that a lot of them can live more than 30 years. But before the study was done it was believed that some of those species only lived for 20 years.

While this method can seem a little rough, in reality, it’s not. Here is a link to a study done by the University of North Carolina, which also has pictures of the marks, and an in-depth explanation of how they work and where they are placed: Box Turtle Collaborative Tier 3: Mark Recapture Study.

Final Thoughts

Those are the most reliable methods to tell the age of a turtle. Unfortunately, they are not all 100% exact, and the ones that are exact are not exactly practical. But that’s the best we’ve got. Even scientists who study turtles use the ring counting method to guess the age of a turtle.

I hope this article helped you in finding the age of your turtle. But in case you still have questions or you would like some help, don’t hesitate to ask in the comment section below, I regularly check the comment sections and answer all questions.