Average Bullmastiff Size And Weight
From Puppy To Adult

If you’re considering bringing a Bullmastiff puppy home or if you already have one as a pet it’s always good to know what to expect size and weight wise as they grow.

That way, you can make sure you have enough room for the dog as well as enough budgeted for the rather large food bill soon to come your way.

The average adult Bullmastiff is 24 to 27 inches tall and weighs 100 to 130 pounds. Males are usually an inch taller and weigh about 10 pounds more than females. However, it’s also important to consider that Bullmastiff puppies start at 12 inches and 20 pounds and grow quickly.

If you’re interested in getting a Bullmastiff, you should consider how big they can get. Then, you can prepare yourself and your family for the large dog. Keep reading to learn how fast Bullmastiffs grow and how big they can be as adults. Read More Below...

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Cute Bullmastiff puppy


How Fast Does a Bullmastiff Grow?

From about two to three months old, a Bullmastiff can gain six or six and a half inches (15 to 16.5 cm) in height. They can also gain 15 to 18 lbs (6.8 to 8.1 kg) in that time.

However, after three months old, the growth rate slows a bit. They may only gain an inch (2.5 cm) or so in a month, and after six months old, they may only grow half an inch (1 cm) in height.

But they will gain a lot of weight in that time. Each month, the dog can gain about 10 lbs (4.5 kg) until they reach 7 months old. Then, their weight gain rate will slow to about seven or eight pounds (3.1 to 3.6 kg) a month on average.

After a year, the dog will still have another eight months or a year to grow. But they will only grow a few pounds in that time.

When Does a Bullmastiff Puppy Stop Growing?

A Bullmastiff puppy stops growing after about 20 to 24 months. By that age, the dog should weigh around 100 to 130 pounds (45.4 to 59 kg) and be 24 to 27 inches (61 to 68.6 cm) tall.


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Bullmastiff Growth Rate From Puppy to Adult

The Bullmastiff growth rate from puppy to adult can fluctuate. The younger the puppy, the faster they will grow. A puppy can double in size from two to three months old. However, the growth rate drops quickly after that.

If you’re getting a Bullmastiff puppy, prepare for the dog to get a lot bigger. Even if the dog doesn’t get much taller, they will gain a lot of weight.

You should make sure to feed your Bullmastiff puppy enough food to support that growth. That way, you can help the dog have healthy joints and bones.

Bullmastiff Puppy Weight and Height at 2 Months

Males at 2 months of age can grow to about 34 to 36 lbs (15 to 16 kg), and they will reach a height of 12 to 15 inches (32 to 37 cm).

Females can weigh about 30 to 32 lbs (13 to 14.5 kg), and they will be about 12 to 14 inches (30 to 35 cm) tall.

Bullmastiff Puppy Weight and Height at 3 Months

Males at 3 months old can weigh between 37.6 to 42.9 lbs (17.1 to 19.5 kg), and they will reach a height of 18.5 to 20 inches (47 to 50.8 cm).

Females will weigh between 34.4 to 40 pounds (15.6 to 18 kg) and will reach a height of 18.5 to 20 inches (47 to 50.8 cm).

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Bullmastiff Puppy Weight and Height at 4 Months

Males at 4 months old can weigh between 48 to 55 lbs (21.8 to 24.9 kg) and will reach a height of 20 to 22 inches (50.8 to 55.9 cm).

Females will weigh between 44 to 52 lbs (20 to 23.5 kg) and will reach about 19 to 21 inches (48.3 to 53.3 cm) tall.

Bullmastiff Puppy Weight and Height at 5 Months

Males at 5 months old can weigh between 58 to 66.3 lbs (26.3 to 30.1 kg) and will reach a height of 21 to 23 inches (53.3 to 58.4 cm).

Females will weigh between 54 to 62.5 lbs (24.5 to 28.3 kg) and will reach a height of 20 to 22 inches (50.8 to 55.9 cm).

Bullmastiff Puppy Weight and Height at 6 Months

Males at 6 months old can weigh between 69.5 to 77.3 lbs (31.52 to 35 kg) and will reach a height of 21.5 to 23.5 inches (54.6 to 59.7 cm).

Females will weigh between 63.8 to 74 lbs (29 to 33.6 kg) and will reach a height of 20.5 to 22.5 inches (52.1 to 57.2 cm).

Bullmastiff Puppy Weight and Height at 7 Months

Males at 7 months old can weigh between 74 to 85.5 lbs (33.5 to 38.8 kg) and will reach a height of 21.5 to 23.5 inches (54.6 to 59.7 cm).

Females will weigh between 68 to 82 lbs (30.8 to 37.2 kg) and will reach a height of 20.5 to 22.5 inches (52.1 to 57.2 cm).

Bullmastiff Puppy Weight and Height at 8 Months

Males at 8 months old can weigh between 82 to 93.4 lbs (37.2 to 42.4 kg) and will reach a height of 22 to 24 inches (55.9 to 61 cm).

Females will weigh between 75 to 87.8 lbs (34 to 39.8 kg) and will be about 21 to 23 inches (53.3 to 58.4 cm) tall.

Bullmastiff Puppy Weight and Height at 9 Months

Males at 9 months old can weigh between 89 to 98.6 lbs (40.4 to 44.7 kg) and will reach a height of 22.5 to 24.5 inches (57.2 to 62.2 cm).

Females will weigh between 80.4 to 92 lbs (36.5 to 41.7 kg) and will reach a height of 21.5 to 23.5 inches (54.6 to 59.7 cm).

Bullmastiff Puppy Weight and Height at 10 Months

Males at 10 months old can weigh between 92.3 to 104.8 lbs (41.9 to 47.5 kg) and will reach a height of 22.5 to 24.5 inches (57.2 to 62.2 cm).

Females will weigh between 84 to 99 lbs (38.1 to 44.9 kg) and will reach a height of about 21.5 to 23.5 inches (54.6 to 59.7 cm).

Bullmastiff Puppy Weight and Height at 12 Months

Males at 12 months old can weigh between 102 to 118 lbs (46.3 to 53.5 kg), and they will reach a height of 23.5 to 25.5 inches (59.7 to 64.8 cm).

Females will weigh between 93 to 110 lbs (42.2 to 49.9 kg) and will be about 22.5 to 24.5 inches (57.2 to 62.2 cm) tall.

How Big Does a Bullmastiff Dog Grow?

A male Bullmastiff can weigh 110 to 130 pounds (50 to 59 kg) and reach a height of 25 to 27 inches (63.5 to 78.6 cm).

A female Bullmastiff can weigh 100 to 120 pounds (45.4 to 54.4 kg), and they'll reach a height of 24 to 26 inches (61 to 66.04 cm).

Final Thoughts...

While not the largest dog breed, Bullmastiffs can get pretty big. Be sure to consider their size and growth rate before you bring one home. That way, you can prepare for your dog to reach its adult size.

Here's Even More Bullmastiff Information...


  1. Mastiff Guide Home
  2. Bullmastiffs Dog Info
  3. Average Bullmastiff Size And Weight From Puppy To Adult