Snapping Turtle Age By Size Calculation [With Chart]

The information is current and up-to-date in accordance with the latest veterinarian research.

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Determining the exact age of a snapping turtle is itself a challenge. Of course, you can ask the shopkeeper. But there is little hope that the store has kept track of the age of all its turtles. So, what can you do? Close your eyes, and follow the traditional ways of finding out snapping turtle’s age, for example, by size calculation.

Snapping turtles show a narrow range of size distribution at a particular age. Compare your snapping turtle’s current growth with the standard size-age distribution chart. The chances are you will get a reliable answer on how old your pet is.

These traditional methods hardly provide you with an exact age. Why is that? Also, what are some other ways of determining a snapping turtle’s age? Read through the article to find your answers.

How To Determine Snapping Turtle Age By Size Calculation?

Snapping turtles have an envious lifespan and, at the time, a healthy growth rate. The alligator snapping turtle can reach 32 inches in carapace length over its century-long life. On the other hand, another subspecies, the common snapping turtles, grow 22 inches and have 50 to 75 years of longevity.

It is possible to determine a snapping turtle’s age by measuring its size. Well, at least, this is the belief of some experts. They think snapping turtles share the same size distribution at around a particular age.

I am adding two charts showing the growth of both snapping turtle subspecies at different age points,

Common Snapping Turtle Size Chart

AgeCarapace Length
Hatchling1.5 inches
1 year old3.5 to 5 inches
2 years old6.5 inches
3 years old5.3 to 6.1 inches
4 years old4.7 to 9.4 inches
5 years old6.1 to 8.3 inches
6 years old7.6 to 8.8 inches
10 years old10 inches
15 years old14.3 inches
20 years old14inches++
35 years old14 inches++

Alligator Snapping Turtle Growth Chart

AgeCarapace LengthWeight
Hatchlings1.5 inchesfew ounces
1 year2.5 to 4 inches1 to 2 pounds
2 years5 to 6 inches
3 years6 to 8 inches
5 years old8 to 10 inches
10 years old10 to 12 inches10 to 35 pounds
15 to 2012 to 16 inches35 pounds++
40 years old16 to 26 inches++46 pounds (female)
50 years old16 to 26 inches++64 pounds
80 years old16 to 26 inches++100 pounds
100 years old16 to 26 inches++125 to 175 pounds (male)

N.B. I have collected the chart information from family, friends, online forums, and research papers. It is impossible to conclude anything from observing the growth of only one snapping turtle. Hence, I have researched different sources and come up with the closest size range at an age.

Your snapping turtle may or may not have similar growth. There is nothing to worry about as long as the pet is active, enjoying its food, and has a sound sleep cycle. How to maintain a healthy weight of a snapping turtle? Here is how.

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While one group emphasizes the determination of age by size calculation, most experts differ on the topic. According to the second group, age and size share a vague link. A recently published paper supports this belief.

According to the study, the relationship between age and size is more visible and reflectable when the snapping turtles are hatchlings or juveniles. The link gets weaker as the turtles reach adulthood or approach old age.

The paper also says that male snapping turtles have faster growth than females. Body development of males accelerates from the age of 5 to 7 years old and continues even after 35 years.

The growth takes a heavy fall after 20 years for a female snapping turtle. Are you still struggling to determine the gender of your snapping turtle? Find the easiest tutorial of sexing your turtle here.

Why does the relationship between age and size get weaker? Or why do turtles stop growing after a certain point? The genetics, physique, surrounding, diet, care level or breed, etc., might be responsible for this.

How Can You Tell How Old A Snapping Turtle Is?: Alternative Methods

Unfortunately, not too many techniques are available to determine the age of a snapping turtle. If you remove the size calculation method from the list, you are left with only 3 other options. Honestly, none of them are 100% accurate.

Here is a brief discussion on the alternative age determination ways,

1. Age Determination By Counting Annuli Rings

Like trees, snapping turtles form growth rings each year. The fact can be surprising for some people, but it is true.

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Look at the scutes on the snapping turtle’s carapace. You will find circles making peace with each other and not crossing the scute boundary. Determining the turtle’s age is possible from those very rings if you know the trick.

However, we should have the minimum idea about how the annuli ring works before getting into the calculation.

The rings on the snapping turtle’s scutes share a link to its growth. It means that if the creature is growing, so will the circles.

Now, turtles do not experience the same body development throughout the year. In the summer season, the snapping turtles have abundant food. They can also take advantage of their hunting skills to collect the meals. Hence, a thicker and more visible growth ring forms during summer.

Again, like most other turtle species, winter is not the favorite of the snapping turtles. They struggle to cope with the cold and spend the season hibernating. Even if the turtles do not hibernate, they survive with an insignificant amount of food.

The development of the turtles slows down during the winter. So, the forming growth ring is narrow and vivid.

Each year, two newly formed rings add in the scute, one narrow and light, and another thick and visible. The pair resembles one year of the turtle’s growth. So, if you count all the growth rings and divide them by 2, you will get your turtle’s age.

Here is a summary,

  • Select a scute
  • Count all the growth rings in the scute
  • Divide the number by 2
  • The result indicates your snapping turtle’s age

Hence, if a scute accommodates 16 rings, the turtle is 8 years old.

Unfortunately, this method is not that reliable either and is not always practical. Experts believe you will get a closer guess for the first 7 to 8 years. But then the rings overlap, and it becomes tough to count them all.

Again, the wild turtles often experience shell tearing or wearing due to the predator attack. And so, you can not get a clear picture of the growth rings within the scutes.

2. Shell Appearance

Do you know the shell appearance of a snapping turtle changes with its growing age? Though it can not tell you the exact age, you will have a good idea of its group.

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Take the snapping turtle hatchlings as an example. The babies have ridges running on the center carapace. Again, you will also find white dots on the upper shell.

As these babies grow older, the ridges disappear from the carapace, and so do the white spots. If you meet a medium-sized snapping turtle without any keels on the center, it means the creature is either juvenile or young adult. This way, you can assume the pet’s age group by observing the shell.

3. Skeletology

Scientists have observed traces of growth rings on the bones of aquatic and semi-aquatic turtles. With the help of these rings and some other experiments, the experts can actually determine the approximate age of a snapping turtle.

However, the bone examination or skeletology is not a practical way to determine snapping turtle age for the owners. Only scientists and researchers have access to this technology.

Can You Tell A Snapping Turtle’s Age By Size?

You can make an educated guess at the snapping turtle’s age by calculating its size. Determining the exact age is nearly impossible with this method.

Snapping turtles can have unpredictable growth. While the average growth range for alligator snapping turtles is 14 to 20 inches, some creatures grow into 32 inches.

The same thing happens with the common snapping turtle. The expected growth for common snapping turtles is 10 to 20 inches, but many easily reach a carapace length of 22 inches.

See, you can not predict the development rate of your turtle. Some snapping turtles experience fast growth because of the balanced food, excellent care, or genetics. Again, many turtles might now grow as you expected due to heredity, disease, or poor habitat management.

The experts have failed to pull off an ideal snapping turtle growth chart due to the above reasons. However, you need not worry about your turtle’s size as long as the pet is healthy and doing fine.

How Big Is A 1 Year Old Snapping Turtle?

A baby snapping turtle is not more than 1.5 inches and weighs a few ounces. The hatchlings go through a fast growth at the primary stage.

At the end of the 1st year, the snapping turtle baby gains a carapace length of 2.5 to 4 inches and weighs 1 to 2 pounds. Till now, the largest 1-year-old snapping turtle was 5 inches long.

How Big Is A 50 Year Old Snapping Turtle?

The estimated weight of a 50-year-old snapping turtle is 64 pounds, and the carapace might grow 16 to 26 inches or more.

A team of researchers trapped 3 wild alligator snapping turtles back in 2014. The 40 years old female turtle in the group was 46 pounds in weight. Experts have recorded the data and predicted the growth of a 50-year-old turtle.


Determining the age of a snapping turtle by size calculation can be a disaster. Unfortunately, no method is perfect enough to provide you with the exact result. The best way to count your turtle’s age is to mark its birthday. Lastly, be attentive and extra cautious while handling the snapping turtles, or you can lose your fingers.

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About Author

Muntaseer Rahman started keeping pet turtles back in 2013. He also owns the largest Turtle & Tortoise Facebook community in Bangladesh. These days he is mostly active on Facebook.


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