Mastiff

Calm and good-natured, guards by presence not aggression.
A Mastiff
Photo: ocean yamaha
Adult male
73–104 kg
160–230 lb
Adult female
54–77 kg
120–170 lb
Lifespan
9 yrs
Class · Watchdog
also Companion

What it's like

The Mastiff is massive and heavy-boned, with a deep, broad chest and a broad, square head. Its muzzle is short, and the mask, ears and nose are dark. The short, close coat is fawn, apricot or brindle. By nature it is calm, dignified and good-natured with its household, while staying watchful and reserved with strangers. It tends to guard by its presence rather than by aggression.

Day to day
Activity
Happy with modest walks
Intelligence
Easy-going, simple routines
Handler demand
Needs steady training
With people
Affection
Affectionate on its own terms
Loyalty
Sticks close to its people
Independence
Cooperative, with its own ideas
Around the home
Sensitivity
Hardy, takes a busy home in its stride
Voice
Quiet
Prey drive
Usually fine with small pets
Breed explains only about 9% of how individual dogs differ in behaviour1. Meet the dog. A good breeder breeds for temperament as well as health, and matches each puppy's personality to the right home2,3.
Is a Mastiff right for you?
Take the breed matcher

Living with one

It has a short coat. It sheds through the year rather than in big seasonal moults. Plan on a brush once a week. It needs a moderate amount of exercise compared with other breeds.

Size and growth

A Mastiff is a giant dog, heavier even than a Great Dane. Males end up clearly heavier than females. It is one of the heaviest giant breeds.

Puppy growth

Reference curve · community data appears as owners log
By about 5 months, a male Mastiff puppy is already as heavy as a grown German Shepherd. They grow fastest between 5 and 6 months old. They keep growing past their first birthday, longer than a Beagle does. The chart follows Mastiffs themselves, not a general size band. Most males grow into the size large-breed puppy foods are made for.
Fully grown
15 mo
Both sexes, at 99% of adult weight7
Male
Female
Shaded: expected range
0501001502m4m6m9m12m18m
0501001502m3m4m6m9m12m18m
Age
Male
Female
2 months
12.7–18.3 kg 28.0–40.3 lb
9.5–13.5 kg 20.9–29.8 lb
3 months
18.5–26.6 kg 40.8–58.6 lb
13.8–19.6 kg 30.4–43.2 lb
4 months
25.7–36.9 kg 56.7–81.4 lb
19.3–27.3 kg 42.5–60.2 lb
5 months
34.0–48.9 kg 75.0–107.8 lb
25.5–36.1 kg 56.2–79.6 lb
6 months
42.5–61.1 kg 93.7–134.7 lb
31.9–45.2 kg 70.3–99.6 lb
7 months
50.4–72.4 kg 111.1–159.6 lb
37.8–53.5 kg 83.3–117.9 lb
8 months
57.0–81.9 kg 125.7–180.6 lb
42.7–60.5 kg 94.1–133.4 lb
9 months
62.0–89.1 kg 136.7–196.4 lb
46.5–65.9 kg 102.5–145.3 lb
10 months
65.6–94.3 kg 144.6–207.9 lb
49.2–69.7 kg 108.5–153.7 lb
11 months
68.1–97.8 kg 150.1–215.6 lb
51.0–72.3 kg 112.4–159.4 lb
12 months
69.7–100.2 kg 153.7–220.9 lb
52.3–74.1 kg 115.3–163.4 lb
15 months
71.9–103.3 kg 158.5–227.7 lb
53.9–76.3 kg 118.8–168.2 lb
18 months
72.4–104.1 kg 159.6–229.5 lb
54.3–76.9 kg 119.7–169.5 lb

Health and lifespan

In UK lab records, the conditions below turn up more often in Mastiffs than in crossbreeds. Bone cancer and blood-vessel cancer of the skin stand out as far more likely. The most serious are bone cancer (far more likely) and mouth melanoma (much more likely), and both can shorten a life. These are figures for the breed as a whole, not a prediction for your dog.
Listed by likelihood level, highest first, then by how serious it is, then by name.
  • Bone cancer
    Lab-confirmed cases
    Far more likely
    Impact: life-limiting
  • Blood-vessel cancer of the skin
    Lab-confirmed cases
    Far more likely
    Impact: serious
  • Mouth melanoma
    Lab-confirmed cases
    Much more likely
    Impact: life-limiting
  • Skin melanoma
    Lab-confirmed cases
    Much more likely
    Impact: moderate
Lab-confirmed: compares dogs whose tumour samples went to a lab with dogs seen in general practice, so the figures run higher than vet-record ones.

Flat face and breathing

The Mastiff is one of the flat-faced breeds. In UK vet records, flat-faced dogs were more likely to have breathing and airway problems than dogs with a medium-length muzzle, and lived shorter lives on average. Noisy breathing at rest is worth raising with a vet.

Lifespan

In UK vet records, the typical Mastiff lived to about 9 years, shorter than the typical giant breed. Flat-faced breeds as a group live shorter lives than breeds with a longer muzzle.

Where it comes from

The Mastiff's kind of heavy guard dog is recorded as already present in Britain when the Romans invaded, and some were shipped to Rome for the arena. Under the Normans it was widespread enough for the French word dogue to pass into English. It almost vanished from Britain in the years after the Second World War, and imported stock rebuilt it4.

The Mastiff served for centuries as the guard of English estates and farmyards. It was often kept chained by day and let loose at night to deter poachers and thieves. It was also used for baiting bears and bulls until Parliament banned such sports in the eighteen-thirties. Lyme Park in Cheshire kept its own line of mastiffs for generations, and according to a family legend one stood over its wounded master, Sir Piers Legh, at Agincourt. Nineteenth-century breeders set out to fix a consistent type, and the Old English Mastiff Club was founded in the eighteen-eighties. After the Second World War, dogs from North America helped to restore the breed in Britain. Many of them descended from earlier English exports. A mastiff is recorded among the dogs that came over on the Mayflower.

Breed standard

The Mastiff is judged against standard no. 264, in group 2, Pinscher and Schnauzer, Molossoid and Swiss Mountain Dogs4.

Questions people ask

General guidance for dogs rather than a measured Mastiff figure: most females have a first season somewhere between six and fifteen months, and cycles then settle to roughly every 180 days. Smaller breeds tend to start earlier and larger ones later, so a giant breed is most likely at the late end.

Compare with related

Saint Bernard
Pinschers & molossoids · Giant
Great Dane
Pinschers & molossoids · Giant
Bullmastiff
Pinschers & molossoids · Giant
Cane Corso
Pinschers & molossoids · Giant
Or compare the Mastiff with any breed you choose
Track your own Mastiff
Log a minute a day and watch them sit on these curves. Free.

Sources

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Parts of this page were written by AI ·