Pet Care Blog

English Mastiff Size Guide: Growth Chart By Puppy Weight/Age

Dr. Lila Batiari
Small Animal Relief Veterinarian
english mastiff puppy

English Mastiffs are a variation of the Mastiff dog breed, a group composed of giant dogs whose tragic history has earned an unfair stereotype. Though these dogs were initially bred for the gruesome sport of dogfighting, their temperament is gentle, loving, and patient. Some may feel intimidated by the massive English Mastiff size, but these hard-working dogs excel in civic duty on police teams, search-and-rescue missions, and beyond.

If you are the lucky pet parent to one of these noble, protective dogs, you may be asking yourself how big do English Mastiffs get and at what age do they stop growing?

Here’s everything you need to know about the English Mastiff growth rate by weight and age:

English Mastiff Growth & Weight Chart

Age Male Weight Female Weight
1 mo 5 - 20 lb 5 - 15 lb
2 mo 20 - 35 lb 15 - 30 lb
3 mo 35 - 55 lb 30 - 50 lb
4 mo 50 - 70 lb 40 - 60 lb
5 mo 60 - 90 lb 50 - 80 lb
6 mo 80 - 110 lb 60 - 90 lb
7 mo 110 - 140 lb 75 - 100 lb
8 mo 120 - 160 lb 85 - 115 lb
9 mo 130 - 170 lb 95 - 125 lb
10 mo 140 - 180 lb 100 - 140 lb
11 mo 145 - 190 lb 105 - 150 lb
12 mo 150 - 200 lb 110 - 160 lb
24 mo 160 - 230 lb 120 - 170 lb

Please remember that the above numbers are estimates for how much your English Mastiff may weigh by month. All puppies will vary in how quickly they grow, and some puppies will weigh a bit more or less than others.

If you notice your English Mastiff is significantly behind or ahead of the above numbers, we recommend consulting with your veterinarian to make sure your pup is growing appropriately.

How big do English Mastiffs get?

According to the American Kennel Club1, a full-grown English Mastiff male should stand at least 30 inches tall (2 ft. 6 in) at the shoulder. The size of an English Mastiff female at maturity should be at least 27.5 inches (~2 ft. 4 in.) at the shoulders.

Both male and female English Mastiffs should be symmetrical, powerful, and have a rectangular shape.

english mastiff puppy side profile

How much do English Mastiffs weigh?

On average, a full-grown English Mastiff male weighs between 160 and 230 pounds, while a full-grown female weighs between 120 and 170 pounds.

When are Mastiffs full-grown?

Most dogs of this breed will be close to their adult height around one year old2. However, English Mastiff puppies require two to three years to fill out and finish maturing.

Unlike small to medium dogs, giant dog breeds can take years to finish growing. Use our English Mastiff weight chart above to help you monitor where your pup is at in the growing process and to make sure they fall within a reasonable range.

How big should an English Mastiff puppy be at six months?

At just six months old, male English Mastiffs will weigh as much 80 to 110 pounds. In contrast, the average English Mastiff female puppy will weigh 60 to 90 pounds.

Pro Tip: The American Humane Society estimates that one in three dogs get lost during their lifetime. Read more about the cost of microchipping dogs to help your pup find their way back to you should you become separated.

How much bigger will my English Mastiff get?

There are several ways to estimate the size of an English Mastiff at maturity:

  1. Age. A critical factor in estimating how much bigger your English Mastiff will get is their current age. If they are already two years old, they are likely to be close to their final size. However, if your puppy is only six months old, they have substantial growing left to do. Reference our English Mastiff size chart above for more information about how much larger your pup may grow.
  2. Paw Size. Paw size isn’t an exact science. However, if your puppy’s paws look oversized next to their legs and body, it’s a good guess that they are still growing into their paws and filling out. If their paws don’t look oversized, your puppy may be close to their final size already.
  3. Gender. A puppy’s gender will significantly affect how much they end up weighing and how tall they are. Giant dog breeds, like the English Mastiff, have especially prominent differences in how much a male and female dog will weigh.
  4. Parents. Your puppy’s parents are a good indicator of how big he or she may grow to be. Pups rarely outgrow their mom or dad, whichever is largest. If you can reach out to the breeder of your English Mastiff puppy, ask them for more information about the size of their parents and how big past litters turned out to be. This background information will give you a more concrete idea of how big your Mastiff might get when they reach full maturity.

english mastiff portrait

How long do English Mastiffs live?

The life expectancy of an English Mastiff ranges between six and 12 years. Unfortunately, like all purebred dogs, Mastiffs are at increased risk for a number of genetic health issues, such as:

According to the Mastiff Club of America4, cancer is the leading cause of death in English Mastiffs. The most common types include lymphoma, osteosarcoma, and mast cell tumors.

While you can’t alter your dog’s susceptibility to certain conditions like cancer, you can provide them with top-notch veterinary care, which can prevent certain diseases and help to change the outcome of diagnosed health problems.

Are English Mastiff vet bills expensive?

As pet parents, it's important to be aware that veterinary care can be expensive, especially for emergency treatments or ongoing care for chronic conditions. For example, English Mastiffs are prone to cancer, especially osteosarcoma, an aggressive cancer of the bone. Canine osteosarcoma treatment costs can be high, with some cases adding up to over $10,000.

Like all giant dog breeds, the English Mastiff size plays a significant factor in the cost of veterinary care because they will require larger amounts of medications, anesthesia, chemotherapy, and so on compared to smaller dog breeds. It's important to be prepared financialy for unexpected sicknesses and injurties, but less than 20% of pet parents say they could cover $5,000 in veterinary bills up-front, out-of-pocket.

Consider enrolling your furry friend in a pet insurance plan now before any signs of illnesses start. Pet insurance reimburses you for up to 100% of out-of-pocket veterinary care costs so that you can focus on what’s truly important: your English Mastiff puppy’s health and happiness. Dogs that are insured are covered for new illnesses or health conditions they develop and emergency veterinary costs, such as hospitalizations and surgery.

Pro Tip: Pet insurance plans can help dog owners save money on veterinary bills. Check out the options for English Mastiff health insurance now so that you can rest easy knowing your Mastiff will have access to gold-standard veterinary care throughout their lifetime.

Key Takeaways

  • English Mastiffs are giant dogs that can easily weigh as much as an adult man.
  • Male English Mastiffs typically weigh between 160 and 230 pounds, while females usually weigh between 120 and 160 pounds.
  • English Mastiffs are more prone to cancer and certain genetic conditions.
  • Veterinary care costs for English Mastiffs can be costly due to their large size and the cost of additional medications, anesthesia, or chemotherapy needed to treat them.
  • Pet insurance gives you a safety net should your English Mastiff pup need emergency treatment in the future.


  1. American Kennel Club, “Official Standard of the Mastiff” Accessed Sept. 21, 2021
    1. Mastiff Club of Victoria, "About the Mastiff" Accessed Sept. 21, 2021
  2. Veterinary Centers of America, “Mastiff Dog Breed” Accessed Sept. 21, 2021
  3. Mastiff Club of America, “Mastiff - Canine Cancer” Accessed Sept. 21, 2021

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Dr. Lila Batiari, DVM

Dr. Lila Batiari
Small Animal Relief Veterinarian

Lila Batiari, DVM is a relief veterinarian located in San Diego, California. She has a special interest in nutrition, pain management, and surgery! Dr. Batiari enjoys working with Pawlicy Advisor to help others avoid everyday situations that some of her clientele experience. She realizes that expensive vet bills for treatment costs could be much easier for patients with pet insurance.

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