Understanding Bullmastiff growth and development is essential for potential owners of this impressive breed. So, when do they stop growing?
At around 18 months, a Bullmastiff reaches close to its full height and weight. It can still fill out a bit more with muscle after that, but for the most part, the majority of their growth happens in their first year of life.
You can get a good idea of the potential for growth of a Bullmastiff by the size of their same-gendered parent, their paw size, and how big they are compared to the average for their age.
There’s also quite a bit to look at regarding diet, exercise, and health concerns. So let’s take a look.
How Big do Bullmastiffs Get?
The Bullmastiff will grow to a relatively large weight even by three months old after their first growth spurt. They are nearly fully grown by 18 months. They can continue to grow and fill out until two and a half.
We can look at the expected height and weight of a Bullmastiff at different ages to better understand their growth.
Here are the measures for a male Bullmastiff:
- 3 months is 18.5-20” and 38-43 pounds
- 6 months is 21.5-23.5” and 70-77 pounds
- 1 year is 23.5-25.5” and 102-118 pounds
- 1.5 years is 24-26” and 105-121 pounds
“As you can see, even in the early months, a Bullmastiff is relatively large and grows considerably in weight from three months to one year.“
However, its height remains fairly static after its initial growth spurt from 2 months to 3 months.
The expected height and weight of a female Bullmastiff at:
- 3 months is 18.5-20” and 34-40 pounds
- 6 months is 20.5-23.5” and 64-74 pounds
- 1 year is 22.5-24.5” and 93-110 pounds
- 1.5 years is 23-25” and 98-114 pounds
Female Bullmastiffs follow a similar growth pattern to the males except with slightly lower overall numbers.
They also gain most of their height by three months and then gain most of their weight from three months to a year.
If your Bullmastiff continues to gain substantial weight after a year and a half, there may be a cause for concern.
Similarly, if they are not gaining much weight between three months and a year. There are can a variety of health and genetic reasons why this is the case.
Why do Some Bullmastiffs Grow at Different Sizes?
Bullmastiffs are interesting in that they tend to grow to almost their full height within three months. That’s pretty exceptional for dog breeds and can give you are a solid indication of how big they will be in adulthood from a very young age.
Genetics is the most significant factor in how big a Bullmastiff will get, just like with humans.
Since we can’t see directly into their DNA, we can’t know how big they will get, but some tricks can help.
First, looking at how big their parents are is an excellent indicator of the general overall size you can expect. A Bullmastiff is very likely to grow to the same size as its same-sexed parent.
“Another trick you can use is to compare the average height and weight for their age and gender to how big they are at that time.“
This is not quite as reliable, as the timing of their growth spurt can be different from other Bullmastiffs. But, if they are smaller than average or larger than average, this can indicate that they are going to stay that way.
Finally, you can look at their paw size. The paws tend to be close to fully grown, even from two or three months.
And so, more oversized paws compared to their body indicate that they still have a lot of growing to do.
What is the Average Weight and Height of a Bullmastiff?
According to the American Kennel Club Bullmastiff Standard, a fully grown male Bullmastiff has an average height of 26 inches and a weight of 120 pounds.
A female Bullmastiff has an average height of 25 inches and a weight of 110 pounds.
These are only estimates according to breeding standards. There is no guarantee that Bullmastiffs will follow these measures, and of course, many don’t follow the average but are smaller or larger just by luck.
Height is generally a bit more stable than weight, but both have ranges. It is always important to remember that every dog is different—none of these numbers are set in stone.
Environmental and genetic factors can all play a role.
Is it possible for a Bullmastiff to Grow Again after they have Stopped?
After about a year and a half, it is unlikely a Bullmastiff will achieve any further growth.
However, if their growth has slowed considerably before that age, there might be cause for concern and still time to help them grow to their full potential.
There can be dietary or health reasons why they’ve stopped growing prematurely. This includes parasites such as worms, poor diet, or other diseases. However, they may continue growing again if the problem is taken care of.
Can I help my Bullmastiff Grow Taller or Bigger?
For the most part, not really. Their genetics are what primarily determines their final height and height.
So the main thing you can do if you are looking for a taller or bigger Bullmastiff is to look for one with bigger and taller parents.
You could look for indicators that they will grow to the same size, such as their paws and size compared to the average from birth.
There are things you can do to prevent anything terrible from stunting their potential, though.
Good health and diet play a huge role in maximizing your dog’s full potential.
When they are a puppy, it’s essential to feed them healthy and nutrient-rich puppy food.
Then, when they reach adulthood, you can switch out their diet for adult dog food.
The other thing to look out for is health concerns.
Parasites and diseases can severely stunt a puppy’s growth. So if they aren’t looking well or not eating right, check with a vet if there are any health concerns and see if they can be taken care of.
How Much Exercise Should a Bullmastiff Get Each Day?
Bullmastiffs need a bit less exercise than other large dog breeds. They are happy with 30 to 45 minutes of exercise per day. This should include both a daily walk and some strengthening activities.
Joint problems are a major concern for Bullmastiffs, so strenuous exercise can be dangerous when they are young. They also tend to be a bit lazy.
These can make it difficult to know the best way to handle exercise with Bullmastiffs. You need to push them a bit past their laziness but not too much to hurt their joints, especially when they are puppies.
What Type of Diet Should you Provide your Bullmastiff?
For larger dogs, a protein-rich diet is often the best choice. As a puppy, they should be eating at least 20-25% protein and 8% fat.
This provides a strong foundation for them. Grain and vegetables will also be a part of their diet, but you should avoid fully starch-based dog food. Of course, a diet rich in vitamins and minerals is also essential.
High-quality puppy kibble that meets this requirement is a great place to start. Look for some nice real meat ingredients in the list, and check for those protein and fat percentages.
Does a Bullmastiff’s Size Affect its Health?
The significant factors of their size that affect their health come down to their joints and how they can overeat.
Because they grow from small to large so quickly, their joints can be harmed as puppies. They need a nutrient-rich diet for their bones and muscles, plus their exercise needs to keep too much strain away from their joints.
“Overeating, followed by strenuous exercise can also lead to bloat.”
Bullmastiffs tend not to want to do too much exercise, so this is less of a problem for them than other breeds.
However, if they do overeat and then go for a hard walk or play rigorously, the gases from the foods can bloat their stomachs and lead to shock and even death.
Since they need a lot of calories to grow when young, one of the safest solutions is to provide them with regular smaller meals, maybe 3 or 4 in a day.
Final thoughts
Bullmastiffs are wonderful partners in life that grow up really fast. Unfortunately, there isn’t much you can do about their growth, but we’ve gone over a few things that keep them happy and healthy.
Diet, exercise, and of course, genetics all play a role in the growth and general well-being of the Bullmastiff.
