When Do Boston Terriers Stop Growing?

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Boston Terriers are the true definition of cute and cuddly, especially when they are small. You might originally adopt a Boston Terrier because of their small size, but how long do they actually stay small, when do Boston Terriers stop growing, and how big do they end up getting?

When Do Boston Terriers Stop Growing?

Boston Terriers stop growing between 12 to 14 months, which is when they reach their last stage of puppyhood (or adolescence). Their weight normally ranges from 15-25 pounds, depending on their size. Because of their size, Boston Terriers stop growing and maturing faster than large dog breeds.

Graphic image of a black and white Boston Terrier with a text explaining that Boston Terriers stops growing when they reach 12-14 months

How Big Will Your Boston Terrier Grow to Be?

Boston Terriers are generally classified as a smaller dog breed. They have three weight categories:

  • Under 15 pounds (7 kilograms or less). These are the smallest Boston Terriers
  • 15 – 20 pounds (7 – 9 kilograms)
  • 20 – 25 pounds (9 – 11 kilograms)

Boston Terriers are short but sturdy dogs. They can range anywhere between 15 and 17 inches tall.

One great way to determine when your Boston Terrier will stop growing is to consult the breeder you bought your furry pal from. If you adopted a purebred AKC registered puppy from a breeder, the breeder will be able to approximate the size to which your little pup will grow. This is done based on the dog’s family tree and how other members of the family grew.

If you didn’t buy your dog from a breeder or aren’t sure if it is a purebred, you can consult your veterinarian to find out about what size your dog should be. Your veterinarian can approximate the size of the dog at full growth based on their growth trajectory.

It is important to note that female Boston Terriers develop much faster than their male counterparts. They, therefore, reach full maturity much faster. However, the females are often slightly smaller than the males.

The average height of male Boston Terriers is 17 inches with an average weight range of 15 to 25 pounds. The average height of female Boston Terriers is 16 inches with an average weight range of 10 to 20 pounds. Males typically take up to 14 months to reach full maturity.

Stages of Boston Terrier Puppy Development

Whether your Boston Terrier is a pure breed or not, there are various stages of development that your puppy will go through on their journey to full maturity. It’s important to be aware of these stages and how to meet your pup’s needs.

A white Boston Terrier walking along the street

Boston Terrier Growth Stages

Growth Stage Duration Notable Change
Neonatal Birth to 2 weeksEyes start to open
Transitional Two to three weeksAbility to move and play
Socialization Three to 12 weeksResponse to auditory stimuli
Juvenile Three to six monthsDeveloped sexual interest and motor skills
Adolescence Six to 18 monthsChange in energy and temperament
Adulthood 18 months and beyondFull body growth

Neonatal Stage: Birth to 2 Weeks

Boston Terriers experience the fastest growth in this stage. It is important for the puppies to be with their mother during this period as they depend on her for warmth and food. 

The mother is also responsible for ensuring that the puppies defecate and urinate. She will keep them clean as they are not yet able to crawl to a different location to pee or poop.

The puppies’ eyes begin to open for the first time on the tenth day after birth.

Transitional Period: 2- 3 Weeks

The puppies’ eyes are now open and they are getting used to this. They are now able to move on their wobbly legs to defecate and urinate away from where they normally lay. Puppies begin to exhibit social behaviors including playing with each other, growing and wagging their tails.

They begin to respond to auditory stimuli as their ears are also open. They will also begin eating other foods and drinking water out of a dish. They still however, rely on their mother heavily for nourishment.

Socialization Period: 3- 12 Weeks

Puppies begin to bark for the first time. They also react to stimuli such as loud noises. This stage is in fact crucial for determining how your puppy will react to social situations as well as stimuli when mature. Socialization of the puppies at this stage will have an impact on how they respond to humans in the future.

It is important for the puppies to be exposed to as many stimuli as possible during this stage. This includes different noises, smells, weather, and people. A well socialized dog will have greater confidence.

Most puppies are ready for adoption at 8 weeks which is the latter half of this stage of growth.

Juvenile Stage: 3- 6 Months

This is what teenage years are to humans. The puppies are almost at their full size and their sexual interest begins to peak. The dogs develop their final set of adult teeth and will have well developed motor skills.

An adult Boston Terrier dog carrying a red frisbee with its mouth

Socializing is also important at this stage as well as exposure to different stimuli. In addition, it is vital to discuss options for spaying or neutering with your veterinary at this stage for the long term health of your dog.

Adolescence: 6-18 Months

Your puppy has entered young adulthood at this stage. They will be more energetic and aggressive. They are likely to be testing boundaries and will therefore often be disobedient. You may see all the hard work you put into training seem to go downhill. Stay the course and know that this stage will soon pass.

18 Months and Beyond

The adolescent stage ends at about 18 months and the Boston Terrier enters adulthood. You can breathe a sigh of relief as your dog is now fully mature and has most likely stopped growing. 

If you want to know for sure, you can check their ribs cage for knobby plates. Run your hand down the rib cage to feel these plates. If you can still feel them, their ribs are still developing and haven’t filled out completely.

Frequently Asked Questions

Why Is My Boston Terrier So Small?

Generally, the smallest a Boston will be is about 15 pounds. If you find that your pup is smaller than this (such as 10 pounds), it is considered a “mini” Boston Terrier and could end up developing health issues as it grows. Check with your local veterinarian if your dog is not growing larger than 10 pounds.

How big is my Boston Terrier puppy going to be?

Related Questions

How to Tell How Big My Boston Terrier Will Get?

To estimate how big your Boston Terrier will be, note your puppy’s weight at 16 weeks, then double the number. Add a pound if it’s a male. This measurement is a good ballpark weight for your adult pet.

How Does Spaying and Neutering Affect Growth in Boston Terriers?

Early spaying and neutering can affect your Terrier’s growth hormones, preventing your pet from growing fully. It’s best to wait for at least two heat cycles to let the hormones settle down before spaying or neutering.

Why Is My Boston Terrier So Small?

Your Boston Terrier may be too small due to a lack of calories in its diet. Consult a vet about nutrition issues to determine the best dog food to help your Terrier grow.


Boston Terriers are generally a small dog breed that is good natured and cheerful. The time between birth and maturity with Boston Terriers is quite short. You should therefore enjoy every moment of it.