How Big Does an English Mastiff Get? The Complete Growth Timeline

The English Mastiff is a giant canine whose growth happens very rapidly. In getting this dog, you must know what to expect when it comes to his size so you can evaluate if your home space is adequate to welcome him or if you need more sturdy furniture to accommodate his adult weight.

Photo from: fronkythemastiff (IG)

So, what is the forecasted size of the dignified English Mastiff? By the time he reaches maturity, the average height ranges from 27-35.8 inches. The male Mastiff has an average weight of 195 pounds whose zenith can be over 30 inches while the female can reach a norm of 145 pounds with a minimum height of 27.5 inches. 

Although this dog breed is assumed to grow large in a short period, a possibility should be considered such as some pups in the litter will have a slower growth pace than the rest. This should not always be a subject of concern as each dog is an individual.

To learn more about the English Mastiff’s development and maturation, let’s observe all size-related information through this article. 

Do English Mastiffs Grow Quickly?

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Yes, they do. With a calculated life span of 6-10 years, the Mastiff breed has all of its life stages squeezed into it. However, several factors can come into play making it impossible to exactly conclude how quickly an English Mastiff will grow. 

Differences in growth rate are more obvious for large dog breeds compared to smaller ones. The English Mastiff’s measurement involves several inches while a dog such as a Chihuahua only has at least 6 inches to quantify.

Also, the reason why there are no absolute expectations for an English Mastiff’s development period is that the smaller puppies in the litter might have a spurting growth later in life and those who were born bigger might mature slowly.

The best way you can do to project the size of your Mastiff is by referencing the size of the dog’s parents and grandparents. However, this remains to be an unreliable overview. 

At What Period Do English Mastiffs Stop Growing?

At about 18 to 24 months, your English Mastiff puppy will reach its full potential size. The moment he completes the period, he’ll continue growing until he’s about 4 years old. However, the added growth on this stage is not as obvious as it was during his puppyhood. 

Additionally, by the time an English Mastiff turns 2, his estimated mass would be 205 pounds for males and 135 pounds for females. 

The Growth Timeline of an English Mastiff

Monitoring your English Mastiff’s growth is essential for various reasons such as health. Since there is an estimated size for every stage of this dog, you would be able to easily assess if your pet is on the right track like if he’s underweight or overweight or if he’s suffering from a physical condition that prohibits him from growing normally. 

The table below will show you the average weight a male and a female Mastiff will get depending on age:

AgeFemale WeightMale Weight
2 months16 to 32 pounds21 to 37 pounds
3 months29 to 49 pounds35 to 55 pounds
4 months40 to 60 pounds50 to 70 pounds
5 months50 to 80 pounds65 to 95 pounds
6 months65 to 95 pounds85 to 110 pounds
7 months75 to 105 pounds110 to 145 pounds
8 months85 to 115 pounds120 to 160 pounds
9 months95 to 125 pounds135 to 175 pounds
10 months110 to 145 pounds145 to 185 pounds
11 months114 to 152 pounds149 to 185 pounds
1 year120 to 160 pounds150 to 200 pounds

The table below will show you the average height a male and a female Mastiff will get depending on age:

Age Female HeightMale Height
2 months11 to 13 inches12 to 15 inches
3 months13 to 17 inches14 to 17 inches
4 months15 to 19 inches16 to 20 inches
5 months16 to 20 inches18 to 22 inches
6 months17 to 21 inches19 to 24 inches
7 months17.5 to 22 inches20 to 25 inches
8 months18 to 23 inches21 to 26 inches
9 months18.5 to 24 inches22 to 27 inches
10 months19 to 24 inches22.5 to 27 inches
11 months23 to 25.5 inches24.5 to 28 inches
1 year20 to 26 inches25 to 29 inches

Of course, the growth timeline provided is simply a guide and is not an absolute standard for every English Mastiff dog since the growth rate varies. To see if your large dog has normal growth progress, giving him regular vet check-ups regarding his height and weight can be done.

How Big Are English Mastiffs When Fully Grown?

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When an English Mastiff reaches his full size, the average size given by the American Kennel Club (AKC) says that it would range from 120 to 230 pounds and a height of 27.5 inches and up.

To see a clearer distinction between the two genders, the male is going to be much taller and heavier than the female English Mastiff. He can easily reach 160 to 230 pounds with a height that exceeds 30 inches after 48 months. In the same given amount of time, the female Mastiff will accumulate 120 to 170 pounds with a height that ideally starts at 27.5 inches and over.

These given statistics are merely just based on the observation which involved several English Mastiffs for the sole purpose of giving Mastiff owners a certain idea on what to expect when their dog stops growing or when the canine reaches a certain age.

Although the commonly available information regarding a Mastiff’s size is always the average, know that you will still have instances wherein you’d meet a dog of this kind who surpasses the ideal height. Moreover, some dogs will also weigh heavier than expected such as Aicama Zorba whose mass reached 343 pounds!

Check if your English Mastiff’s Weight is Healthy

Although it is quite impossible to determine what the right weight a Mastiff should have, every Mastiff parent should at least focus on two things in ensuring that the dog remains healthy: food and activity level. 

This dog breed is prone to laziness and obesity so these are what an owner should always deal with seriously. Even though you cannot give the English Mastiff a vigorous exercise, having no daily drills at all can take a toll on the canine’s body. 

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The amount of calorie intake this large dog should have must be based upon the level of his energy. If you notice that your four-legged companion becomes a couch potato and seems to just keep on preserving his energy, giving him large portions of meals will make him heavier and could hurt his joints. 

On the other hand, an English Mastiff who is active and gets to receive inadequate meals will lead to him becoming underweight. This must also be considered a serious health risk despite the fad in us, humans, thinking that being thin is in. 

For dogs, becoming underweight would change a whole lot of processes in their metabolic state. Once fed in the right amounts, they will suffer the ‘refeeding syndrome’ that can cause coma, muscle weakness, fluid retention, and heart problems. 

The best thing you can take for your good-natured dog is by being alert if sudden changes occur regarding his size and mass. There could be underlying issues that need to be treated so contact your vet right away if concerns arise.

Factors That Can Affect Your English Mastiff’s Growth

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The whole physical development process of every English Mastiff puppy largely depends on the kind of owner he ends up with. This is why owning a dog is more than just having a companion. He would forever be reliant on what you can give him, but of course, his growth will also be affected by other factors.

Let’s see what major areas should every English Mastiff parent hit as targets in raising the largest canine.

Food & Diet

A high-quality dog food considered to be complete and balanced can establish a healthy life for a Mastiff pup. If he receives all the nutrients needed for his growth, he will be less likely to experience any health issues that are often caused by the lack of certain vitamins and minerals in the body. 

Mastiff pups only need a few months before they transform into their huge dog size. With that, providing them twice the amount you would feed an adult Mastiff is a prerequisite. They have large appetites! However, even though they eat a lot, you still shouldn’t overfeed them. 


Exercise will not disrupt the growth process of a Mastiff. But, his massive weight incorporated with a strenuous daily drill can disturb and damage his growth plates and long bones. If this happens, his bone development will turn out abnormal and will eventually lead to major joint issues.

To aid your lovely Mastiff to grow up healthily, simply take him out for a walk and avoid making him run. His weight that keeps causing pressure to his legs can result in injury.


Ever wonder why many dog enthusiasts encourage potential dog owners to see the pup’s parents first? This is because the dog’s heritage will be a great determining factor on how your Mastiff will end up like. 

By getting a female Mastiff, her size can be based on her mother. As for the male one, the father would be the reference. 

This will not always be right, but puppies usually end up looking like their parents.

Health Issues

Hypothyroidism is very common in dog breeds including the great English Mastiff. If by any chance, your dog suffers from this condition, he will be more lethargic, less energetic, and gain more weight. Meanwhile, diabetes mellitus can cause rapid weight loss. 

These health problems have to be diagnosed as early as possible. If you notice a sudden increase or decrease in terms of your dog’s body mass, visit your local vet immediately.


It is a commonly accepted fact and norm that a male Mastiff will be larger than his female counterpart by about 40 to 70 pounds and an edge of at least 3 inches in height. Even if the female’s parents have reached their maximum ideal weights, she will remain smaller than the other puppies in the litter. 


Roundworm or hookworm infections can stunt your pet’s growth. These pests can be contracted either from external environments or even from the mother herself. When a heavy infestation occurs, all the nutrients don’t go directly to the dog’s well-being but rather are devoured by the foreign organisms inside your Mastiff’s body.

Other bad results manifest such as your dog has poor coat quality, a bloated stomach, obvious rib cage, and diarrhea.

Closing Thoughts

How your English Mastiff grows is influenced by controllable and uncontrollable factors such as health, food, genes, and gender. Getting a pup from a reputable breeder is a good start towards puppy-owning. Providing him the best lifestyle you can afford which will encourage him to also be in his excellent state would be the next step.

Remember that going for an English Mastiff means bigger food supply, bigger toys, and more care needed to be granted. If these are no problem to you, go ahead and bring home your adorable Mastiff puppy!