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Home > Turtles > How Big Do Box Turtles Get? Average Weight & Growth Chart

How Big Do Box Turtles Get? Average Weight & Growth Chart

Box Turtles

The box turtle is a native North American reptile that lives in the United States and Mexico, known for their characteristic, dome-shaped shell and flat plastron, which can grow between 5–7 inches in diameter. An adult box turtle may weigh up to 2 pounds, but they can be as light as half a pound (8 ounces).

The box turtle navigates their world quietly and slowly. They are relatively long-lived when you compare them to other pets of a similar size.


Facts About the Box Turtle

The box turtle is a member of the Emydidae family, which includes reptiles that live in both aquatic and terrestrial environments. Their defining feature is their shell, which acts as a unique form of protection. As reptiles, they exist primarily in the warmer parts of the planet. However, they are a diverse group of animals that live in a broad range of habitats with varying diets.

The box turtle is one of the more popular reptilian pets. As long as you give them what they need, you’ll have a pet that will live a relatively long time. Many of the box turtles that you find in pet stores are native to South Carolina. However, the number of wild turtles has dwindled in recent years, putting a halt to these practices.

Box Turtle Size and Growth Chart

Age Average Shell Length
Hatchling 1–2 inches
6 months 2 inches
1 year 2–3 inches
2 years 3–3.5 inches
3 years 3–4 inches
4-6 years 5–7 inches

Biggest Factors Impacting Box Turtle Growth

Like many animals, male box turtles are larger than females. Therefore, the sex of your pet is a significant factor among the many that you must learn to manage. Another critical one is your box turtle’s living conditions. In nature, these reptiles live in warm and often humid areas.

Box Turtle in its habitat eating meal worms
Image Credit: SusImage,Shutterstock

UVB Exposure

The best housing for box turtles replicates the wild with a large aquarium or similar enclosure that stays warm and reduces drafts. Box turtles also require a UVB light. This will help them synthesize vitamin D, which is essential for growth. About 12 hours a day is necessary to give them enough exposure.

Box turtles typically spend their days basking in the sunlight, which the UVB light replicates with wavelengths of 290 to 320 nanometers. Check the product description to make sure that it meets this essential requirement.

Dietary Factors

Box turtles are omnivores, which means that they eat both plants and meat or insects. They require the right mixture of vitamins and minerals to grow. Critical nutrients are protein, calcium, and phosphorus. Protein provides the necessary building blocks, or amino acids, to make bone and other tissues.

Calcium and phosphorus have a special relationship. The ideal ratio is 1:1.666. If a box turtle’s phosphorus intake is too high, it can interfere with calcium absorption and thus, the adult animal’s size. Other vital nutrients include fiber, vitamin A, and vitamin B1. Remember that box turtles forage in the wild for a wide variety of foodstuffs that you must replicate when you keep them as pets.


The box turtle’s genetics plays a significant role in the animal’s size. It is a direct reflection of the health and size of their parents. If they were small, it’s likely that their offspring will also share this trait. That’s why diet is such a critical factor for ensuring proper growth.

Eastern Box Turtle
Image Credit: Mark_Kostich, Shutterstock

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Can I Tell My Box Turtle’s Age Just From Their Shell?

It’s possible to get a general idea of a box turtle’s age by counting the rings, or scutes, on their shell. Like many animals, turtles grow rapidly at first, which is evident in the visible scutes. Growth often slows for up to years at a time, however. That fact is apparent with narrower bands that are difficult, if not impossible, to count.

A box turtle reaches their adult size at 5–7 inches. These animals can live 10 or more years, with some reaching 20 or more years. Genetics limits their growth beyond this point. However, normal wear and tear can make them smaller. Other factors also come into play, such as diet and age.

Why Isn’t My Box Turtle Growing?

Three things may affect a box turtle’s growth rate. The first is biological. Growth goes on pause during the animal’s lifetime and may last for years at a time. The second reason relates to diet. Like all organisms, a box turtle depends on a supply of raw materials to fuel growth. If their nutritional intake is inadequate, the reptile won’t grow and will stay in a suspended state until things change for the better.

The final thing to consider is the box turtle’s UV exposure, which is crucial for growth and calcium absorption. We suggest verifying that the light over your pet’s cage does indeed provide the right wavelength spectrum. Using a standard incandescent lightbulb isn’t going to give the necessary exposure.

Eastern Box Turtle
Image Credit: Lisa Holder, Shutterstock

The Lifespan of Box Turtles

Box turtles kept as pets typically live longer than those in the wild. After all, there is less chance that a predator will kill them. Their living conditions are also more stable than living outdoors. As long as you take care of their needs for temperature, humidity, and light, your box turtle can live up to 20 years. Some even make it past 30 years.


Final Thoughts

Box turtles are fascinating animals that make an excellent choice for a pet for older children. The best way to care for them so they reach their optimal size is by paying attention to their housing and diet. These things will ensure that the reptile’s body has everything that it needs to grow. There isn’t much wiggle room with these things, so it’s imperative to invest in the best cage and care for the health of your pet.

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Featured Image Credit: allyartist, Pixabay

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