How Big Do Jack Russell Terriers Get

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The personality traits and hunting instincts of Jack Russell Terriers make them good hunting companions, watchdogs, and family dogs. However, it’s important to consider the size before adopting one, especially if you live in a studio house or an apartment. So, how big do Jack Russell Terriers get?

How Big Do Jack Russell Terriers Get?

Most Jack Russell Terriers (JRTs) have a standing height of 10-15 inches and weigh around 13-17 pounds. In most cases, adult male Jack Russell Terriers are slightly bigger and heavier than their female counterparts.

The dog’s size varies depending on the ancestral history and whether the dog is purebred or mixed.

Cute JRT dog chasing football

Adult JRTs are considered undersized and underweight if they are less than 10 inches tall or weigh less than 13 pounds. On the other hand, you can consider your Jack Russell Terrier oversized or overweight if it is more than 15 inches tall and weighs more than 17 pounds.

Keeping in mind that these are only average sizes and weights, the following health, age, sex, and genetic factors determine the dog’s actual size and weight.


Like any other dog, JRTs attain their maximum size and weight during adulthood. Regardless of the sex of your JRT, the following are some of the sizes you can expect your dog to have at different ages.


Puppies around three months old weigh around 6-8 pounds. On the other hand, puppies about six months old weigh around 11-14 pounds and have a standing height of 10-12 inches.

At around six months, you might start to notice a slight difference between the size of male dogs and female dogs. Usually, male puppies are on the higher side of the size and weight range.


Although most JRTs can be regarded as fully grown from 6-8 months, the dog might continue growing bigger and gaining muscles up to when it’s around 12 months old.

Adult JRTs have an average height of 10-15 inches and weigh around 13-17 pounds. Typically, JRTs retain this size and weight range in their larger part of life.

Cute Jack Russell gazing from afar


Regardless of the age, the type of food you feed your JRT directly impacts the overall size and weight of the dog. Although the signs of malnourishment might not be noticeable in the short term, malnourishment leads to stunted growth.

Keeping in mind that there is a balance between size and weight, malnourished puppies end up being smaller and underweight adults. That means the healthy weight of such adult dogs will be below the average of 13 pounds.


Under the same conditions, male JRTs tend to be slightly larger and heavier than females. Usually, it is because male dogs have larger bone and muscle mass as well as larger skeletal size. However, female dogs attain their maximum weight and size earlier than their male counterparts.


The gene combination in a JRT can impact how big it grows. Under the same conditions, it is not uncommon to find some JRTs becoming taller than others, depending on their ancestry. That means you can use the size of the dog’s parents to predict your dog’s future size and weight.

How to Ensure Your Jack Russell Terrier Attains the Optimal Size and Weight

Considering that JRT size and weight can vary depending on the diet and ancestry history, you can use the following tips to ensure your dog is within the right height and weight range.

Standing JRT back view
  • Feed your dog a balanced diet: In most cases, stunted growth results from failing to feed the puppies nutrient-rich foods. It’s advisable to feed the puppies foods rich in amino acids, minerals, and vitamins.
  • Adopt the dog from a reputable breeder: You can avoid genetic disorders that cause size issues by adopting the dog from a reputable breeder. Typically, you will access the pedigree documents and see the parents’ size.
  • Deworm the dog: Your dog might have stunted growth even after feeding it nutritious foods due to parasites. If you suspect your dog might be having a worm infection, contact your vet for a checkup.

Related Questions 

How Big Can a Jack Russell Terrier Mix Get?

The size of a JRT mix will depend on the size of the other parent and which genes are dominant. For instance, if the dominant genes are from the JRT parent, the dog can be around 10 to 15 inches, just like purebred JRTs. Otherwise, it will be almost the same size as the other parent.

How Do I Measure the Height of My Jack Russell Terrier?

You can measure the height of a JRT by measuring the distance from the ground to the highest point of the wither. The dog should be standing like a square with all the feet standing naturally and well-balanced on the ground when taking the measurements.

Final Thoughts

Although adult Jack Russell Terriers have an average height of 10-15 inches, being slightly shorter or taller than this isn’t an issue. However, if the dog weighs less than 13 pounds or more than 17 pounds, your dog is underweight or overweight and needs diet adjustments.