When Do Jack Russells Stop Growing

When Do Jack Russells Stop Growing?

If you find this fierce dog is the perfect fit for your family and plan on bringing a Jack Russell puppy into your home, you may wonder how this small breed develops throughout puppyhood. 

Continue reading to learn about the growth rate and stages of Jack Russell puppies. You will also learn about their physical attributes and how to keep them healthy so they can grow to their proper size. 

What Age Does A Jack Russell Stop Growing?

Jack Russells tend to grow to their full height between six and eight months old, but they continue to fill out and gain weight until they are a year old.

Genetics will be one of the main factors in determining the physical build of your Jack Russell puppy.

Jack Russells tend to be around the same size as their parents, so if you are curious about how big your dog will be, find out the size of their father and mother. 

If you bought your puppy from a reputable breeder, you could also inquire about how large other puppies have grown in past litters. 

Diet and exercise also play a role in your Jack Russell’s growth. A malnourished puppy will be undersized and not reach its full growth potential.

Make sure you feed your Jack Russell puppy nutritious food and ensure that they get lots of exercise. 

Jack Russell Sizing And Physical Characteristics

Both male and female Jack Russell Terriers range between 10 to 15 inches tall and weigh 13 to 18 pounds.

Males tend to be larger than females and will likely fall on the higher end of these height and weight ranges. 

Jack Russells are mainly white and can have tan, brown, black, cream, or tricolor markings. This breed has a short coat length that comes in three different categories: smooth, rough, and broken.

Due to their hunting history, they also have a thick and coarse double coat that is prone to shedding.

All of these coat types need minimum grooming and will just require a weekly brushing of your dog. 

Jack Russell Growth Chart

This growth chart shows the average heights and weights of Jack Russells at different ages.

These measurements are only ranges and are meant to give you an idea of the growth rate of Jack Russell Terriers.

Some Jack Russells are smaller or larger than these weights and heights, so do not worry if your puppy does not fit into the sizes listed below.

AgeHeightHeight and Weight
NewbornSize of your handMale: 4 – 8 oz
Female: 4 – 8 oz
1 Month OldMale: 2 – 4 lb
Female: 2 – 4 lb
2 Months OldMale: 4 – 6 lb
Female: 4 – 6 lb
3 Months OldMale: 6 – 8 lb
Female: 6 – 8 lb
4 Months OldMale: 6 – 8 in
Female: 6 – 7 in
Male: 8 – 10 lb
Female: 7 – 10 lb
5 Months OldMale: 10 – 12 lb
Female: 8 – 11 lb
6 Months OldMale: 10 – 12 in
Female: 10 – 12 in
Male: 11 – 14 lb
Female: 11 – 14 lb
7 Months OldMale: 12 – 15 lb
Female: 11 – 15 lb
8 Months OldMale: 13 – 16.5 lb
Female: 12 – 16 lb
9 Months OldMale: 13 – 17 lb
Female: 13 – 17 Ib
10 Months OldMale: 13 – 17.5 lb
Female: 13 – 17.5 lb
11 Months OldMale: 13 – 18 lb
Female: 13 – 18 lb
12 Months OldMale: 10 – 15 in
Female: 10 – 15 in
Male: 13 – 18 lb
Female: 13 – 18 lb 

Different Growth Stages For Jack Russells

Jack Russells go through many stages throughout their puppyhood, and each phase is an exciting time to watch your new puppy grow and learn.


When Jack Russell puppies are first born, they are so tiny that they can fit in the palm of your hand and weigh only four to eight ounces. 

Jack Russell’s typically have five to eight puppies in a litter, meaning your puppy will have plenty of company.

During this stage, Jack Russell puppies cannot see or hear. Newborn dogs need to spend most of their time with their mother bonding and growing from the nutrients in her milk.

They also will spend lots of time sleeping and snuggling with their siblings for warmth.


The transitional period of puppyhood lasts from when puppies are 2 to 3 weeks old.

Jack Russell puppies will start to open their eyes and observe the world around them. They also can begin to hear and smell.

During this phase, Jack Russells will still be relatively tiny but will begin to interact with their environment. They will start to wean off their mother and socialize more with their siblings.

If you are around your Jack Russell at this age, you will notice them learn to bark and wag their tails. 


The socialization period begins when your Jack Russell puppy is three weeks old and lasts until they are three months old.

This time is critical in your Jack Russell’s life as the socialization they receive at this age will help form their personality and temperament. 

Jack Russells will first learn socialization skills from playing and interacting with their siblings and mother. Once they go to their new homes, it will be up to the owner to ensure they get proper socialization.

During this phase, your Jack Russell can go through a fear period, which is why it is crucial to expose your puppy to different people, animals, and places. 

Your puppy will also experience rapid growth throughout this period, and both male and female Jack Russells will weigh between six and eight pounds by three months. 


The juvenile stage of your Jack Russell puppy’s life is still crucial for socialization and lasts from when they are three to six months old.

Puppies will reach about two-thirds of their full-grown height and weight during this stage. Jack Russells begin to display their full energy at this age and will be very active.

They also will start to grow their adult teeth.

You must begin training your Jack Russell at this age. Jack Russell Terriers are very intelligent and, despite their stubbornness, can be easy to train with the correct methods. 

You want to make sure training is fun and fast-paced for your puppy since Jack Russells get bored quickly and can easily become distracted.

It is essential to use lots of positive reinforcement and treats during training sessions since terriers are very food-motivated. 


During the adolescent stage, you will notice your Jack Russell puppy start to become much more mentally and physically mature. They also will begin to become more independent. 

Much like a teenager, this time is when your puppy will be mischievous and not always want to listen to your commands.

Jack Russell chasing a ball

You will want to exercise a lot of patience with your puppy, and obedience classes may be helpful for your Jack Russell Terrier at this age. 

This phase typically begins at six months old and lasts from when your puppy turns 12 to 18 months old, depending on the dog. 


While most Jack Russell Terriers are physically mature when they are 12 months old, many do not reach full mental maturity until they are around 18 months old.

Every dog, like people, develops differently, so your dog may reach full adulthood at a younger or older age. 

Since Jack Russells are a very active breed, they tend to have the same energy level as a puppy.

You will want to continue to make sure they get a lot of exercise and playtime so they do not get bored and become prone to destructive behaviors like chewing and digging.  


Jack Russell Terriers are a charming breed with bold personalities. Like all dogs, Jack Russells go through different developmental phases throughout their puppyhood.

With this article’s information and tips, you will be prepared to raise and watch your Jack Russell grow into a happy and healthy adult.