English Mastiff Size Guide How Big Does an English Mastiff Get

Planning to adopt an English Mastiff? You probably know that this is no lapdog (although they might want to be!). The English Mastiff is one of the oldest, most powerful, and largest dog breeds. They’re gentle giants with a calm, affectionate, and good nature. They even get along well with children, making them the perfect family pets. But how big do English Mastiffs get? And at what age are they fully-grown? In this article, we’ll discuss all about the English Mastiff size and growth patterns from birth to adulthood. As an extra bonus, we’ve also created an interactive English Mastiff size chart and growth calculator, which is a helpful tool for anyone trying to predict and track their puppy’s growth. Let’s dig in!

English Mastiff

Our handy interactive puppy growth chart and calculator takes all the hard work out of predicting your puppy’s potential adult size. This helps you to know exactly what you are in for.

Psst! Check Out These Awesome Puppy Things!

English Mastiff Size Predictions: How Big Do English Mastiffs Get?

As you might know, the English Mastiff is one of the largest dog breeds both in terms of height and weight. In fact, the English Mastiff is considered as a giant dog breed with a weight of up to 230 pounds! Not only are they heavy and muscular, but they’re also tall. The average English Mastiff size ranges between 120 and 230 pounds in weight and their height starts from 27.5 inches and can go even beyond 30 inches. 

English Mastiff

It’s important to note that all dogs are unique and it’s not uncommon for some pups to fall slightly above or below the usual breed standards. However, if you’re worried that your dog seems over or underweight, please consult with your veterinarian about possible solutions. Underfeeding your dog can lead to malnourishment and a wide range of health issues. Similarly, overfeeding your dog might lead to obesity, which in turn paves the way for joint problems, diabetes, and heart conditions.

Additionally, this is why it’s particularly important that your English Mastiff puppy gets the correct nourishment he needs to grow that adorable little body into a healthy adult one. Check out these guides on best dog food for puppies here.

Fun Fact: An English Mastiff named Zorba set the record for the world’s largest dog in November 1989. He was eight years old and had a height of 37 inches at the shoulder, he weighed 343 pounds, and he was 8 feet and 3 inches long from the top of his nose to the tip of his tail. Pretty impressive!

Are There Different Sizes Of English Mastiffs?

Although the English Mastiff technically comes in just one size, there’s actually quite a difference between male and female pups. Like with other large and giant breed dogs, male English Mastiffs tend to be taller, heavier, and stockier than females. 

Let’s take a closer look at the average English Mastiff size chart for male and female pups:

Male English MastiffFemale English Mastiff
Weight160-230 pounds120-170 pounds
Height30 inches and up27.5 inches and up
When Full-Grown?24-36 months24-36 months

*A dog’s height is measured from their withers, also known as the shoulder blades.

As we can see from the English Mastiff size chart above, there’s a considerable difference between male and female English Mastiffs. Females tend to weigh between 120 and 170 pounds and usually have a height of at least 27.5 inches measured at the shoulder. Males, on the other hand, can be even up to a 100 pounds heavier than females. On average, male English Mastiffs weigh between 160 and 230 pounds and their height starts from 30 inches. 

English Mastiff Size Charts & Growth Patterns – Month Wise

Just like other breeds, English Mastiffs usually grow fastest in their first 50% of adult weight. This typically correlates to the first 6 months from birth. But compared to some smaller dog breeds, the English Mastiff will already be a large dog at 6 months of age. And although they grow big and fast, they’re still puppies like any other breed at that age. 

Here’s the average English Mastiff size chart by age for a male English Mastiff:

Age3 months6 months9 months12 months24-36 months
Weight35-55 pounds85-115 pounds135-175 pounds150-200 pounds160-230 pounds
Height14-17 inches19-24 inches22-27 inches24-28 inches30 inches

Looking at the English Mastiff size chart above, we learn that by 3 months old this breed has already reached about half its adult height and around ¼ of its adult weight. By 6 months old, their weight has doubled and they’ve already reached over half or even ¾ of their adult height. After that, their growth will start to gradually slow down over time. At 12 months old, English Mastiffs have reached most of their adult height and weight. Although they still continue to gain weight with each passing month, their growth in height will usually plateau around 18 months old. Likewise, by that time, their weight gain has slowed down and happens at a much steadier pace. 

English Mastiff

Eventually, English Mastiffs stop growing somewhere around their second or third birthday. Even though the weight gain isn’t as rapid anymore, they will continue to fill out and gain more girth in this time period. What’s more, it’s not uncommon for some pups to continue gaining weight up until their fourth or fifth birthday. 

Tip for English Mastiff puppy parents: Check out our interactive English Mastiff size chart and growth calculator that predicts your English Mastiff’s full-grown size and lets you track their growth into adulthood. Simply fill in your puppy’s details and our calculator will reveal you the results. 

English Mastiff Size: Frequently Asked Questions

How Big Is A Full-Grown English Mastiff?

A full-grown English Mastiff can weigh anywhere between 120 and 230 pounds. Male English Mastiffs usually weigh between 160 and 230 pounds and have a height of over 30 inches at the shoulder. Female English Mastiffs are somewhat smaller and usually weigh around 120 to 170 pounds. Their height starts from 27.5 inches at the shoulder. 

English Mastiff

You can calculate their potential adult weight at 23 weeks by taking what they weigh at that age and multiplying it by two.

A different formula you could use is:

  1. Growth = current weight / current age in weeks
  2. Adult weight = Growth x 52 (number of weeks in one year)

So, for example, if your 12-week old pup weighs 18 pounds. You simply divide the current weight by their age in weeks and multiply the result with 52:

18/ 12 = 1.5
1.5 x 52= 78 pounds

78 pounds would be the expected weight of your adult-sized English Mastiff.

At What Age Is An English Mastiff Full-Grown?

English Mastiffs usually reach their full-grown size anywhere between 2 to 3 years old. Smaller English Mastiffs tend to reach full maturity sooner than their larger counterparts. However, even beyond the 3-year mark, some Mastiffs might still continue growing. 

To conclude, a gentle giant in its truest meaning, the English Mastiff is a large, but docile dog with a sweet and calm nature. Although their looks can scare many, they’re wonderful companions who are eager to please their people. If you’ve decided that the English Mastiff is the one for you, it’s crucial you know what to expect in all stages of puppyhood. We hope our English Mastiff size guide has been a helpful resource, so you can keep track of your puppy’s growth and development. 

Parents of English Mastiffs: How big is your pup? Let us know in the comments below!

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