Jack Russell Terriers are happy-go-lucky, spry little dogs that bring so much happiness to their owners. If you love little dogs, live in an apartment or smaller living spaces, or are just curious about the breed’s size—we have all the growth facts you could want! On average, a Jack Russell Terrier can weigh up to 13.5 pounds (6 kilograms) and grow up to approximately 12 inches (30 centimeters) in height.
So, without further ado, here is more about this athletic, lively little breed. Will a Jack Russell be the right size for your living space? Let’s see!
Jack Russell Overview
The Jack Russell Terrier is an adorable little dog that is classically white with black and/or tan markings. They can come with a smooth, broken, or rough coat, so the look can be a little different depending on the type of Jack Russell you choose.
Jack Russell Terriers are known for being clownish, energetic, and stubborn! These chipper little dogs are agile, alert, and sociable. They tend to get along well with strangers and other pets, even if they like to rule the roost.
Jack Russells have stout, muscular little bodies with great tone and structure. Typical to the terrier, these dogs are very athletically capable and can jump quite high into the air. They’re the perfect dog to teach a whole bunch of fancy tricks.
Jack Russell Terrier Size and Growth Chart
In the chart below, we are going to explain exactly what you can expect from your Jack Russell from month to month. Keep in mind that this chart shows a list of averages, so not every Jack Russell will be an exact fit on the scale every month. You will find a wide range of sizes of Jack Russells in their adult age, here we have taken into account a dog that will reach about 14 lbs in their final adult size. Your vet is always the one to determine whether your Jack Russell is meeting their weight markers.
| Age | Weight Range | Height Range |
| 0 months | 0.5–1 pound | 2–3 inches |
| 1 month | 1–2 pound | 4–5 inches |
| 2 months | 2–4 pounds | 5–6 inches |
| 3 months | 3–5 pounds | 6–7 inches |
| 4 months | 5–7 pounds | 7–8 inches |
| 5 months | 7–9 pounds | 8–9.5 inches |
| 6 months | 8–11 pounds | 9–10.5 inches |
| 7–9 months | 9–13 pounds | 10–12 inches |
| 12–24 months | 12–14 pounds | 10–12.5 inches |
When Does a Jack Russell Terrier Stop Growing?
A Jack Russell Terrier is considered fully grown by the time they reach approximately 12 months of age. These pups are considered small dogs, so some of them might top out in their growth at around 9 months of age. These little dogs will be very unlikely to continue to grow in size and height past the 1-year marker.
Factors Affecting the Size of Jack Russell Terrier
Is it possible to determine how big an individual Jack Russell will get? Even though there’s a general average, obviously every dog will be different. Some of them will be on the runt side while others will be on the very large side.
You will see a pretty drastic difference if you line them up Jack Russell by Jack Russell. Several factors can affect the height and weight of an adult Jack Russell Terrier, including genetics, age, and overall health.
Genetics
Genetics play a huge role, possibly the biggest, in how large a dog gets. Often, dogs take after their parents, so bloodline speaks volumes. If both parents are smaller, the puppies will likely be on the smaller side as well.
Age
Age speaks volumes about size. Jack Russells typically stop growing at around 12 months of age. Generally speaking, smaller dogs stop growing earlier than larger dogs. Some larger dogs can take upwards of 2 years to