English Mastiff Growth Chart & Weight Calculator

Do you have a Mastiff pup and wonder how tall he or she will grow? Our growth calculator and charts will predict your dog’s adult weight. Simply put in your pup’s weight and age into our calculator and we will estimate the adult size!

Most female Mastiffs grow up to be 120-170 pounds in weight, while males can reach 160-220 pounds!

English Mastiff Weight Calculator & Growth Chart

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english mastiff growth

How big will my Mastiff get?

The above calculator will give you an idea of the expected adult size of your dog. Of course, your Mastiff’s eventual size is dependent on different factors and no two dogs grow at exactly the same rate.

You will find that your Mastiff most likely goes through growth spurts in his first year. During these growth spurts he will eat like crazy (really – a ton of food!) and he might be more sleepy than usual.

When a growth spurt is over your Mastiff is considerably taller – and probably needs a new collar several sizes up!


Your Mastiff’s parents’ size can give you an idea of the weight you can expect your pup to reach when grown up. However, size is a trait that is not passed on predictably: Two large dogs might have small offspring or the other way around. 

If you want to get a better idea of your pup’s future size, consider other relatives in addition to the parents. What size are the aunts and uncles of your pup? How about the grandparents? Does the pup have any halfsiblings or even full siblings from a previous litter? 

The size at birth is not always an accurate clue to the adult size either. The smallest pup out of a litter may grow up to be one of the largest, and the largest pup may end up at the low range of adult size and weight.

Size is especially unpredictable if your pup is a Mastiff mix breed. One parents is a Mastiff and the other is a different breed – than predicting the adult weight becomes even harder.

How long does it take for a Mastiff to be fully grown?

As a large dog, it can take over 3 years for a Mastiff to mature physically.

As a general rule – the smaller a dog is, the faster he will be done growing. On the other hand, the larger and heavier a dog, the longer he grows.

Adult Mastiffs are very large dogs.

Females are 27-32 inches tall and weigh 120-170 pounds. Male Mastiffs can reach a height of 36 inches and weight anywhere between 160 and 220 pounds!

While Mastiffs reach their adult height within the first year of life, they “fill out” in the following 1-2 years. Their chest will get broader and deeper (especially if they are not spayed or neutered). Your Mastiff will also gain a lot of muscle mass.

Interestingly, fawn-colored Mastiffs do not show their final coat color when they are newborn. Not just their size changes – but also their coloring!

Age and Weight

Let’s see how much your Mastiff might weigh at a certain age!

How much does a 6 month old Mastiff weigh?

At 6 months of age, a female Mastiff would weight between 70 and 95 pounds.

A male Mastiff will find his weight between 90 and 120 pounds.

How much does a 1 year old Mastiff weigh?

A female Mastiff will weight between 110 and 150 pounds at her first birthday.

A male Mastiff can be expected to be 140-195 pounds at 1 year of age.