When Do Jack Russells Stop Growing? Explained With Tips

When Do Jack Russells Stop Growing? Explained With Tips

When we buy a new puppy, we always wonder what they will look like when they grow up. But with time, we get used to seeing the puppy every day. Eventually, we miss the minor changes in the doggo’s body! 

So, when do Jack Russells stop growing? Jack Russells stop growing when they are about 6-8 months old. By the age of 1 year, your JRT will be in his maximum size.

Once you finish reading this post, you will get to know all the information about Jack Russell’s growing FAQs. Let’s get started!

What Age Is A Jack Russell Fully Grown? 

Watching our puppy grow up from being a tiny body to a full-grown, handsome, or beautiful one is such a fascinating journey. If you’re maintaining an album or a scrapbook, like me, for your dog, you must know that very well.

It brings many nostalgic feelings when I turn the pages of my doggo’s scrapbook. It shows the full growth story and memories, time well spent. So I urge you to start making one if you haven’t already. 

Now let’s see when our playful little jewel will stop growing. Unlike humans, puppies attain adulthood quite early. Jack Russells stop growing when they are 12 months old.

Although he would be an all-grown doggo at around eight months, there would be many subtle changes in a dog’s body until one year. After that, your puppy is no longer a puppy. He’s a majestic doggo!

When Do Jack Russells Stop Growing?

As I mentioned earlier in the article, a puppy slowly grows up to adulthood until he’s 8 to 12 months old. During this time, make sure the diet, exercise, and training your dog get are excellent.

The dog we raise lovingly is almost like our own child. We have to prepare the perfect environment during the development curve where they could grow into a doggo gentleman with no complications. 

We will have well-grown, perfectly healthy dogs always at our heels when the Jack Russells stop growing. Also, he will have a gleaming fur coat and a permanent set of teeth by this time.

He’ll be alert and always in guard mode, unlike the bubbly, easy-going, playful nature he projected while your baby was still a little puppy.

These factors will help you determine whether or not your Jack Russells gain their full potential size.

Also, with this article, we will inform you about what your JRT will look like when he’s several ages. So that you could perfectly understand his age and health condition.

What Is The Average Size of A Fully Grown Jack Russell?

There’s always a point where our body is maximum; the weight matches our height and age. It applies the same to dogs too.

And, it will be helpful for you to know how grown your Jackie should be when he’s at certain ages.

Thereby, you can determine if there are necessary changes to the diet, exercise, and other variables that affect growth in a JRT. 

It would be best to consider all stages; before and after your Jack Russells stop growing. 

By six months, your dog should be between the average weight of 5.1 to 6.4 kg ( 11.2 – 14.1 lbs). When the doggo reaches eight months, he must be around 5.6 to 7kg ( 12.3 -15.4 lbs) when the JRT terrier stops growing.

Even though this age is the fully developed stage and your puppy won’t grow anymore in height, the weight will continually change until he’s 12 months old.

And of 12 months, your terrier will be at the average weight of 6.4 to 8.2 kg if he’s perfectly healthy. 

From 10 to 18 months, the dog goes through the adolescent stage. He’ll be more active and start showing signs of the need to mate.

So, you should neuter or spay your doggo during this age if you wish. After Jackie passed that age (18 months), he’s officially an adult; a fully grown one. 

When Jack Russells stop growing, they have a height between 10-15 inches with a weight of up to 8-2 kg. During the rest of his life, it’s okay to sway up to 9 kg.

But more than that, your dog will be overweight. But, you can easily avoid it with a proper nutritious meal and daily exercise.

What Affects The Growth of A Jack Russell Terrier?

As I mentioned earlier in the discussion, the growth of a JR Terrier is very similar to that of a human child. This development depends on the daily nutrition intake, exercises, genetics, infections, and other health problems.

Let us see you more about each separately. 

  • Genetics

It is not a big deal or an issue. In straightforward terms, if your puppy’s parents are well built, your puppy will be too. And if they’re small and short, the pup will be small and short.

It will help you to stay out of confusion if you know the build of your puppy’s parents. Thereby you know what to expect when your Jack Russells stop growing.

  • Daily nutrition intake

Just like how human babies will go into development deficiencies if they don’t get the essential nutrients, puppies can be under-developed too.

So rather than any other phase of life, make sure you’re feeding your puppy a balanced meal. Essentially it should be rich in minerals, fatty acids, vitamins, and fiber.

This diet directly affects when trying to gain your dog’s full potential size.

  • Exercises

A proper daily exercise routine of walking, running, and being fully active for 20-30 minutes a day is essential for a dog. Jack Russells, in particular, are very active dogs.

These exercises maintain a healthy metabolism by helping them digest the food and absorb good energy. It prevents your dog’s overweight problems.

  • Health issues

The primary concern here is worm infections. These parasitic worms in the doggo’s body will suck away all the nutrients you give him.

If he’s not property de-wormed and provided the necessary medicines to keep worm infections under control, your doggo won’t reach his full size.

Also, other unsuspecting underlying health issues will delay proper growth. If you have any concerns, check them out with your local vet.

Those are the main factors that affect your Jack Russells growth. We all need our pet to look good when he’s older. Therefore keeping the above factors in check is very necessary.

We hope your doggo reaches his max when your Jack Russells stop growing. There’s no higher pleasure for a dog parent than their pet looking gorgeous.

Thank you for reading this post. Stay tuned with Jack Russell Owner for more interesting posts. Have a nice day!


  • George Brown

    George B. is the founder of the JRO Organization. He believes in creating a better world for domestic animals. He believes domestic animals are more vulnerable than other animals, especially dogs, since they have been used to depending on their owners for generations. So, he started JRO to share his ideas and insights while helping vulnerable dogs worldwide. George runs multiple projects on street dogs in developing countries, especially Sri Lanka.

    [email protected]

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