How Big Are Boston Terriers?

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Boston Terriers appear perpetually short and small, which may leave you wondering: how big are Boston Terriers in their puppy, adolescent, and adult stages? If you are still discovering all there is to know about Boston Terriers, let’s start by understanding how age, sex, health, and care impact their growth.

How Big Are Boston Terriers?

When Boston Terriers stop growing at around 12 to 14 months of age, they should have compact, squarely-proportioned bodies that weigh approximately 10 to 25 pounds. Additionally, they are likely to stand between 16 to 17 inches tall. Male Terriers tend to grow bigger by five pounds compared to their female counterparts. 

Graphic image of a Boston Terrier, weighing scale and measuring tape that explains how big Boston Terriers are

Size Differences in Adult Boston Terriers

The American Kennel Club classifies a Boston Terrier’s weight into three categories: 15 pounds or less, 15 pounds and under 20 pounds, and 20 to 25 pounds. 

After the adolescence phase, which ends at around 18 months of age, Boston Terriers enter adulthood. There is little weight difference between both genders. At this point, the weight may depend on factors such as food intake, exercise, and health status. 

The smallest Terriers can be anywhere from eight to 12 inches long, while the biggest ones may be 22 to 28 inches long. If you want to determine your Terrier’s actual measurements, you need to measure your pet’s weight, neck, length, and chest circumference.

Growth of Boston Terrier Puppies  

One day, Boston Terriers are small enough to fit into your hand. The next moment, they are growing bigger and zooming around the house. Keep in mind that the size depends on the growing stage.  

Boston Terrier puppy

Stages of Boston Terrier Puppyhood

PhaseDurationApproximate Weight 
Neonatal PeriodBirth to around two weeks of age 0.48 pounds
Transitional Period2 to 3 weeks of age2.53 pounds
Socialization Period3 to 12 weeks of age 3 to 7 pounds 
Juvenile Period12 weeks until adolescence 7 to 15 pounds 
Adolescence 6 to 8 months 15 to 19 pounds 

By understanding these phases, I get a better idea of how big Terriers can become. 

  • Neonatal period: You may not witness this unless you’re also taking care of the mother Terrier. During this stage, the puppy’s size results in limited movements. Food and warmth from the mother are crucial to encourage growth. 
  • Transitional and socialization periods: The puppy Terrier starts to open the eyes, move slowly, and make soft noises. The ears also begin to open, so that the puppy may respond to auditory stimuli. Socialization with the parents and siblings will be beneficial for this phase. 
  • Juvenile period: For Boston Terriers, this stage means growing their final set of adult teeth. Once they hit six months, their size lets them obtain close to the same motor skills as adult Terriers would have. They would be hitting sexual maturity, so monitor how your male Terrier plays with female ones. 
  • Adolescence: Some may show disinterest in socializing, while others would have tons of energy to mingle with people and other pets. They would feel the desire to be dominant and mark territories. Terriers are unlikely to be aggressive, although some adolescent ones may exhibit stubbornness.

How a Boston Terrier’s Size Affects Its Way of Living 

The average puppy weighs 12% less than it did a decade ago, making a Boston Terrier’s size the ideal lap dog. Experts believe that more compact homes lead to owners selecting miniature breeds. Terriers don’t require large living spaces to survive, allowing them to adapt quickly to living with families in small living conditions. 

Dog sitting patiently

Moreover, smaller dogs are easier to control. Whether it’s for grooming or daily activities, you have the physical upper hand to make your pet obey. This is favorable if you need to bring your dogs on travels, when you fly or ride a car, you can easily get them in leashes or crates. 

The size also helps a Boston Terrier withstand fun, agility games. Even with a stout body, this breed has strong legs that are great for catching balls and frisbees.

Maintaining Boston Terrier Size 

Puppies have dietary recommendations that aid them in developing a robust and healthy body during various growth stages. Avoid sweetened foods that can cause them to lose appetite and suffer from upset tummies. In addition, make sure that the treats don’t take up 10% of your puppy’s daily food intake.

As they stop drinking milk from the parent Terrier, you would need to introduce them to puppy food formulas gradually. You know you’re doing proper feeding if your dog has normal stools, appropriate energy levels, and a healthy coat.  

In general, the energy density and calorie levels affect your Boston Terrier’s size. This is why it’s essential to provide food that includes high protein content to support the muscles. You can also incorporate moderate fat and fiber to help your pet feel fuller even with small eating portions. 

Aside from that, exercise routines can influence how big your Terrier can grow. It is ideal to dedicate at least 60 minutes of exercise per day to strengthen bones, build up muscle, and lower the blood pressure. 

Boston Terrier big for his age

Related Questions

Before I wrap up, let’s answer more FAQs regarding a Boston Terrier’s growth. 

Are Boston Terriers Small or Medium Dogs? 

The American Kennel Club considers Boston Terriers as small, non-sporting dogs. Dogs from the small category tend to be lap dogs or small versions of working and hunting dogs.

How Will I Know If My Boston Terrier Is Still Growing?

Boston Terriers complete the last stage of puppyhood and adolescence at around 12 to 14 months of age. If you can feel the knobbly plates from your Terrier’s rib cage, then it’s still most likely developing and growing the body. 

Does Paw Size Indicate My Boston’s Full Size?

While a dog’s paw size isn’t an entirely accurate way to estimate your Terrier’s size, it can be an indication of how big your pet will be. Smaller breeds have fairly large paws to support their bulky built. A Boston Terrier’s paw size at three months is usually proportionate to their adult size.  

How big is my Boston Terrier puppy going to be?


Small in stature, yet Boston Terriers are mighty creatures full of love, kindness, and joy. If you are looking for a little furry companion, the size of Boston Terriers may be suitable for you. As you join them in their growth journey, you will also see how their personality evolves. 

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