Skip to Content

The Age Of Snapping Turtles By Size

When you are trying to determine the age of a snapping turtle then you can make a fairly good estimate based on its size – at least if it’s not mature yet. That’s because Snappers grow at a fairly predictable rate, right up until the point they reach maturity.

Once mature, however, their growth rate slows down enough that it won’t be as much use to you. So, how do you determine the age of snapping turtles by size?

In today’s article, we’ll take an in-depth look at the expected rates of growth for both common and alligator snapping turtles, including their mass, and some frequently asked questions on the subject.

By the time we’re done, you’ll have all you need to know to get a pretty good approximation of a snapping turtle’s age!

Not sure how to identify a snapping turtle? Click here to open an article on that very subject in a new window for later!

The Rate At Which Snapping Turtles Grow

Picking up two snapping turtle hatchlings
They’re not as snappy at this age, but just you wait!

The growth rate of the snapper is impressive before they fully mature, although once that happens, their growth rate slows down to almost zero.

You can see a fairly verbose study of this, including a chart, on Researchgate in a paper entitled ‘Estimates of somatic growth rates of common snapping turtles (Chelydra serpentina) in Texas, USA’ by Thanchira Suriyamongkol.

Summing up the report, Chelydra serpentina (the Common snapping turtle) has its highest growth rate between the ages of 0 to 10 years for both males and females.

From age 10 to 20 years, the growth rate is still high but still significantly lower, especially for females. That’s because males tend to stop growing at 25 years, while females stop at about age 15.

To better understand this, we’ll take a peek at a snapping turtle’s growth starting from their hatchling phase and up to adulthood.

The Age Of Common Snapping Turtles By Size

Upon hatching, the size of the common snapping turtle is just 1.1 inches (2.9 cm). At this size, it is a piece of cake to tell their age because they are so tiny. Within its first year, the turtle will increase in mass to become three to five times its original size.

Keep in mind that by size we are measuring the carapace — the turtle’s shell – as this is the most reliable and consistent way to quantify their size.

By the time it is 1 year old, the common snapper hatchling will be 3.5 to 5 inches (8.9  to 12.7 cm) in length.

Over the next one to two years, it sees a significant increase in size, but not as dramatic a change as experienced within its first year. By ages 2 to 3 years, the snapping turtle will have a carapace length of approximately 5.3 to 6.1 inches (13.5 to 15.5 cm).

Over the next one to two years, the common will increase by as much as another 3 to 4 inches (7.6 to 10.2 cm). This brings the carapace length up to 4.7 to 9.4 inches (11.9 to 23.9 cm) by the time the turtle is between 4 to 6 years old.

Over the next five years, the growth rate slows down significantly, and the turtle may increase in size by as little as 1 inch. At 10 years, the snapping turtle’s carapace length is typically very close to 10 inches (25.4 cm) in length.

Common snapping turtle - chelydra serpentina
Older, wiser, and bigger — This is a mature common snapping turtle.

By age 10, the common snapping turtle has reached maturity, and at this stage, it will continue to grow at a significantly reduced rate until its death.

To give you a better idea of how slowly they grow in this stage, Common snapping turtles have a carapace length of 14 to 18.5 inches (35.6 to 47 cm) from the ages of 15 to 40 years.

To sum up what we’ve learned here, you can memorize or print out this handy chart, and this will allow you to gauge a snapper’s age reliably if they are less than 10 years old!

Age (years)Average Shell Length
01.1 inches (2.9 cm)
13.5 to 5 inches (8.9  to 12.7 cm)
2 – 35.3 to 6.1 inches (13.5 to 15.5 cm)
4 – 64.7 to 9.4 inches (11.9 to 23.9 cm)
1010 inches (25.4 cm)
15 – 4014 to 18.5  inches (35.6 to 47 cm)

The Age Of Alligator Snapping Turtles By Size

Outside ponds are a good idea for alligator snappers - they get pretty BIG!
Outside ponds are a good idea for alligator snappers – they get pretty BIG!

The alligator snapping turtle grows to be bigger than the common snapping turtle, but during the first 10 years of the turtle’s life, the growth rate is pretty much the same as with a common snapper.

While the common snapping turtle has a very reduced growth rate when it reaches 10 years of age, alligator snappers will continue to grow — eventually reaching a carapace length of 26 inches to the common snapper’s 18.5.

To accommodate that extra growth information, we’ll take a closer look at the carapace length by age and the alligator snapper’s projected weight.

Carapace Length By Age

Upon hatching, the alligator snapping turtle measures about 1.5 inches (3.8 cm), and over the next year, it almost doubles that — reaching carapace lengths of 2.5 to 4 inches (6.35 to 10.2 cm) by the age of 1 year.

At 2 years old, the alligator snapper has a carapace length of approximately 5 to 6 inches (12.7 to 15.2 cm). This is an increase of about 1 to 4 inches that will vary from turtle to turtle.

By the age of 3, the turtle reaches a carapace length of around 6 to 8 inches (15.2 to 20.3 cm), and over the next two years, that will increase by about 2 to 4 inches. By 5 years of age, you can expect a total carapace length of 8 to 10 inches (20.3 to 25.4 cm).

During the next five years, it’s length will increase by about 2 to 4 inches, and by age 10, the snapper’s carapace is 10 to 12 inches (25.4 to 30.5 cm) long.

At this point, their growth rate slows down considerably, and over the next ten years, it will increase in length by only 2 to 6 more inches. From 10 to 20 years old, they average between 12 to 16 inches (30.5 to 40.6 cm) in total carapace length.

The turtle still continues to grow, even beyond this point, and by the ages of 40 to 50 years, the carapace length will fall between the range of 16 to over 26 inches (40.6 to over 66 cm). The chart below will sum it all up nicely – let’s take a look!

AgeAverage Carapace Length
01.5 inches (3.8 cm)
12.5 to 4  inches (6.35 to 10.2 cm)
25 to 6 inches (12.7 to 15.2 cm)
36 to 8 inches (15.2 to 20.3 cm)
58 to 10 inches (20.3 to 25.4 cm)
1010 to 12 inches (25.4 to 30.5 cm)
10 to 2012 to 16 inches (30.5 to 40.6 cm)
40 to 50+16 to over 26 inches (40.6 to over 66 cm)

Weight By Age

An Alligator snapping turtle is pretty hard to miss when they aren't trying to hide.
An Alligator snapping turtle is pretty hard to miss when they aren’t trying to hide.

You can also estimate the age of the alligator snapping turtle by its weight – provided that you can weigh it safely, of course!

At 1 year of age, the weight of the turtle should be about 1 to 2 pounds (0.4 to 0.9 kg). By age 10, the weight of the alligator turtle will increase by a minimum of about 10 pounds (4.5 kg), so that the turtle be between 10 to 35 pounds (4.5 to 15.9 kg).

Over the next ten years, they will continue to add weight, reaching an average of 35 pounds (15.9 kg) by the time they are 20 years old.  After that, the turtle will continue adding weight until it reaches a 40-year-old weight of around 46 pounds (20.9 kg).

Females normally do not grow beyond a weight of 46 pounds, but Males will continue to add mass, eventually reaching weights between 64 to 176 pounds (29 to 80 kg). We’ll summarize this information below for easy digestion.

Age (years)Mass/Weight (pounds)
11 to 2 pounds (0.4 to 0.9 kg)
1010 to 35 pounds (4.5 to 15.9 kg)
10 to 2035 pounds (15.9 kg)
4046 pounds (20.9 kg)
50+64 to 176 pounds (29 to 80 kg), for males, females remain at 46 pounds

While we’ve covered the two most common snapping turtles today, there are actually 5 different types of snapping turtles – Click here to learn more when you’re done here!

Frequently Asked Questions

How big is a 100-year-old snapping turtle?

A 100-year-snapping turtle will be a massive turtle, as the turtles continue to increase in size slowly throughout their lives.

By way of example, the largest common snapping turtle is a specimen named “Big Snap Daddy”, who at 93 years of age weighs about 90 lb (40 kg).

By contrast, the largest alligator snapper on record was a specimen caught by some researchers at the Shedd Aquarium of Chicago.

It was estimated to be close to 100 years old and weighed a whopping 249 pounds(112.5 kilos).

How old is a 1-foot snapping turtle?

A foot-long (30 cm long) snapping turtle – either a common snapper or an alligator snapper – should be approximately 10 to 12 years of age.

How old is a full-grown snapping turtle?

This depends on the sex of the turtle. Male common snappers reach maturity at age 4 to 6 years, with a carapace length of 7.08 – 7.48 inches (18 to 19 cm), while females take a little longer, reaching maturity between 10 to 12 years of age.

By this time, the female will have a carapace length of 7.87 to 8.66 inches (20 to 22 cm). Keep in mind that these turtles will keep growing after maturity, just at a significantly slower rate.

They will reach their maximum size at age 15 to 40 years for common snapping turtles and age 20 to 50 for alligator-snapping turtles.

The Age of Snapping Turtles by Size: The Conclusion

The size of the snapping turtle may be used to determine its age, but only up until the point that it reaches maturity. This is because their growth rate will slow down significantly once mature, but up until then you can make a pretty accurate estimate.

For best results, simply review the charts we’ve provided today and file the info away in your mind for the next time that you see a snapper at the pet store or a local freshwater body.

As long as it’s not matured, guessing its approximate age should be a piece of cake!

Now that you’re done, if you’re curious how the common and alligator snapping turtle really compare, check out Common Snapping Turtle vs. Alligator Snapping Turtle and we’ll tell you all about it!

Click to rate this post!
[Total: 1 Average: 5]

Sharing is caring!