Whether you are considering adopting a Jack Russell puppy or have already done so, it is up to you to be sure that your puppy is growing into the adult he should be.
To do this, you can use a Jack Russell size chart to help guide you in knowing whether your pup is the right weight.
We have broken down everything that you need to know about a growing Jack Russell Terrier, from when they stop growing to how much you should be feeding your dog.
This is what you need to know to keep your dog healthy.
When Do Jack Russells Stop Growing?
Looking at your puppy, it might be hard to imagine exactly what he will be like as an adult.
Since Jack Russells are not very big dogs, they do most of their growing in the first 36 weeks of their life.
By the time that your dog is 36 weeks, which is about 8 months old, your dog will be around 95% fully grown.
Before he reaches his first birthday, your Jack Russell Terrier will be done growing altogether.
This is the same for both male and female Jack Russells as there is not a noticeable size difference between the two sexes.
Jack Russell Size Chart
Ideally, you can use a Jack Russell weight chart to keep track of your puppy’s weight as he goes. A weight chart works by tracking your dog’s weight based on his age in months.
You will need to have a starting point that tells you where your dog is on the spectrum of averages.
For example, if you know your Jack Russell is 8 pounds at 3 months old, you will know that he is a heavier dog and will likely remain so on his growth curve.
You can then follow that, to predict that he will be about 17 pounds when he is fully grown at 11 months old.
A Jack Russell size chart can also help you see when your pup is not growing as well as he should be.
If you know that he should be 17 pounds when he is full-grown, based on an earlier weight, and he weighs much less, then you might have cause for concern.
If you are worried at all about the amount of weight that your dog is gaining, you need to go to your vet.
Your vet will be able to work out whether there is anything that is causing your dog to go off his growth curve.
Jack Russell Weight Chart
|Age||Average Weight Lbs|
|3 months||6 - 8 lbs|
|4 months||8 - 10 lbs|
|5 months||8.5 - 12 lbs|
|6 months||11 - 14 lbs|
|7 months||11.5 - 15 lbs|
|8 months||12 - 16 lbs|
|9 months||12.5 - 16.5 lbs|
|10 months||12.5 - 17 lbs|
|11 months||13 - 17 lbs|
|12 months||13 - 17 lbs|
Jack Russell Puppy Development Stages
Birth – 2 Weeks
The first puppy development stage for your Jack Russell Terrier is puppyhood. Puppies are very helpless when they are born and require a lot of care and attention.
They will be completely reliant on their mother for milk, so if it seems like the puppy is not gaining enough weight, it might be a sign that the mother’s milk is not enough.
This can especially be the case if it was a large litter of puppies.
3 Weeks – 12 Weeks
After the initial puppyhood phase, your dog will move into the socialization phase. This is when puppies become very curious and can begin to destroy things.
Jack Russells are highly energetic and as a result, get easily bored. You will need to train your puppy and also make sure that you are preventing him from being destructive.
He needs to be stimulated. Since they do not have natural social skills, you need to socialize your puppy to learn patience he doesn’t have on his own.
4 Months – 9 Months
The next phase of development is the juvenile phase. Your puppy will have more energy at this point and will need a lot more exercise to stay happy and healthy.
This means that the dog needs one to two hours of exercise daily. This can be as easy as play in the yard or taking your pup out for walks.
These will need to be moderate walks since your dog is a puppy and you can overexert your dog.
10 Months – 18 Months
Your Jack Russell Terrier will be fully grown before he hits the 12-month mark since most Jack Russells are done growing at 11 months old.
Your dog should be calming down at this point as well, but the breed itself is still a high energy breed and will still need a lot of exercise in order to stay happy.
You should not have to worry about obesity as long as you do not overfeed the puppy.
When your dog is fully grown, he will still have a lot of energy. The dogs can be prone to barking or yapping. They are not a quiet breed.
They are also stubborn and fearless, so training early is so important if you would like to have a good-natured dog later on that makes you happy and does not cause any trouble.
They are a working dog by nature, bred to flush out small animals, and can be bored and restless without the right exercise.
How Big Do Jack Russell Get?
You already know that Jack Russells are not a large breed of dog, so you can expect them to stay small, but if you are hoping to get a better idea of how big your dog will be when he is done growing; there are a few things that you can look at.
A Jack Russell weight chart is a reliable way to track your dog’s growth.
Beyond a weight chart, you can look at the parents if you know them. Dogs will be around the same size and appearance as their parents, so that is a good basis for knowing how big your dog will be.
In bigger dogs, you can look at a dog’s paws to see how much he will need to grow to grow into them. But, since Jack Russell Terriers are small, the paw method is not a good source.
You could also do a DNA test on the dog to see how big his ancestors were and confirm the Jack Russell lineage.
Male Vs Female Jack Russell Growth Chart
When you look at a Female Jack Russell size chart compared to a Male Jack Russell Terrier size chart, you will see that there are some differences.
While when they are fully grown there are not a lot of differences between a male and a female, but they do not grow at the same speed, making it important to look at the appropriate chart to make sure that your puppy is growing at the right speed.
Female Jack Russells grow faster than their male counterparts and will reach their final size sooner.
Typically, males are larger than females, but in a small breed, the size difference is negligible. Both sexes weigh about 17 pounds fully grown.
To weigh your pup, you can weigh yourself while holding your pup, and then weigh yourself again. The difference is your dog’s weight.
You can measure their height by measuring your dog from shoulder to flood while he is standing up.
Will Neutering/Spaying My Jack Russell Affect His Growth?
Most dogs reach sexual maturity sometime between 6 and 12 months of age.
As a result, it became a standard practice to spay and neuter dogs around the six-month mark, when a dog is big enough to handle the anaesthesia but have not yet gone into heat or reached full sexual maturity.
Yet, in more recent years, the new science has shown that there can be complications to having your dog fixed too young.
The new science shows that there dogs can develop joint and movement issues when fixed too young.
This is mostly an issue with large breeds, however, so it might not affect a Jack Russell.
It would be best to talk to your vet to see what she recommends. You do not want any unwanted pregnancies or to have your dog running wild in hunt for mating.
Beagle Vs Jack Russell Size
Both the Beagle and the Jack Russell Terrier have similar colorings and are smaller dogs, but the question is where they compare when it comes to size.
You know already that Jack Russells can be somewhere between 11-17 pounds when they are fully grown. You know that they are prone to barking and are high energy.
A Beagle is larger than a Jack Russell Terrier. While a Jack Russell weighs between 11 and 17 pounds, a Beagle will weigh between 20 and 30 pounds.
Beagles are more howlers than barkers, but also need a lot of exercise to stay happy.
Factors That Affect Jack Russell Growth
Genetics & Gender
When it comes to dog size, the first two factors to go to are genetics and gender.
In most dogs, gender will affect the final size, but that is not the case with a Jack Russell Terrier. Both sexes are the same size.
But they do mimic their parents, so their size is really based on how big their parents and grandparents were. If you have access to your pup’s parents, you can see how big he will be.
Proper nutrition is incredibly important for all growing puppies. During the first year, your dog is getting better strength within his bones.
If your dog is malnourished, there might not be any visible size differences on the outside, but his bones will weaker on the inside, causing size issues and joint issues later in life.
Since the breed is small, you will not likely see anything wrong on the outside, but his movement will be affected.
Physical Activity & Health
Finally, physical activity and health can affect your Jack Russell Terrier’s growth and final size.
If your dog does not receive enough exercise, he could become overweight, which will put too much pressure on your dog’s bones.
Likewise, a dog that is unhealthy will not be able to grow as well as one who is healthy and it could lead to a lot of issues as the dog ages.
How Much To Feed A Growing Jack Russell Puppy?
It is true of all puppies that you need to be able to feed them well in order for them to grow well. But, knowing how much to feed your puppy, you will be able to keep your puppy’s weight on track.
A feeding chart would be the best idea to be able to monitor how much your pup needs and is eating.
But, you also want to feed your dog often enough. Ideally, your puppy would get four equal meals throughout the day, which can be reduced to three at three months, and down to two at six months.
Looking at puppy kibble, your puppy needs 1 to 1 ½ cups of food a day, starting at 8 weeks.
The amount will not change much as your puppy ages, but you will need to switch to adult food when your dog hits his first birthday.
How To Tell If Your Jack Russell Is Underweight Or Overweight?
In the early days of puppyhood, your dog will have a roly-poly belly that makes it tricky to know whether he is underweight or overweight.
But, as he ages, you will be able to visually see whether he is too thin or too big.
A dog that is underweight will have visible ribs. You should be able to feel them, but not see them.
If your dog has gone out of the chubby phase and he still seems to have a round waist that is not defined, he might be overweight. You can also see if your dog has fallen off of his growth curve.
If it seems like your dog is not on track as far as weight goes, you will want to chat with your vet about it. Do not put your dog, especially a puppy, on a diet without talking to your vet first.
The same goes if your dog is too thin. There could be something else at play that has nothing to do with the food or the amount he is being fed.
Do not assume that you are not exercising or feeding him well and fix it; talk to your vet about it.
How To Properly Weight My Jack Russell?
It is a good idea to weigh your growing Jack Russell Terrier every week or every other week while he is growing.
This is how you will be able to keep track of whether your dog is staying on the growth curve or if he has fallen off of it, based on the Jack Russell growth chart.
To weigh your dog, as we mentioned earlier, it is easiest to weigh yourself first, while holding the dog and jot it down.
Then, weigh yourself a second time, without the dog. The difference in the two weights will be how much your dog weighs.
This will work throughout your life, because the dog is usually going to stay under 20 pounds, even when fully grown.
Jack Russell Genetics And Common Health Problems
As much work as you put into keeping your Jack Russell healthy, you will likely still have to battle against genetic conditions.
They will normally happen to purebred dogs, but it can happen to even mixed breeds.
A Jack Russell Terrier is prone to a neuromuscular disease that is known as Congenital myasthenic syndrome.
This disease appears early in life, as soon as 6 weeks. The symptoms will be pretty obvious, because your dog will not be able to collapse and seem very weak.
Another condition that the breed is prone do is hereditary ataxia, which is a gait disturbance caused by malformations.
There is also a pulmonic stenosis possibility, which is an obstruction of blood flow from the heart and can be very serious and fatal.
You can talk to your vet about the possibilities for any of these conditions and see what you can do to help prevent them from becoming fatal or shortening the lifespan if you are able to get on top of them.
Some of these things can be managed and the dogs will live normal and healthy lives.
Most conditions will not show up until much later in life, so you will not know what you are getting right away.
A Jack Russell Terrier is a wonderful and lively breed to adopt, but you need to be able to give him the care that he needs. The puppies are high energy and need a lot of exercise to stay happy and healthy.
They do grow quickly and do not get very big, so you will need to really watch to make sure that your dog is growing well.
You can do this by using the Jack Russell weight chart, keeping track of whether your dog is growing consistently.
Given their high energy and love of barking, make sure that you are able to give a Jack Russell the care he needs before adopting one.