KENAI
Mastiff

The breeds · working

AKC Working · UKC Guardian · FCI standard 264

Mastiff.

RKC: the Mastiff (once the Old English Mastiff) was employed as a guard dog, a gamekeeper's dog and a hunter of wolves, and for bear and bull baiting; the pits were outlawed in 1835. UKC: a long history as a fighting dog, protector of the home, and use against other animals and as a weapon in war; in America now a devoted family pet that may serve as a protector mainly by its imposing size. FCI utilization: watch and security dog. AKC standard temperament: grandeur and good nature, courage and docility; dignity rather than gaiety. AKC history feature: modern DNA research shows no single prototype mastiff spawned all heavy-boned breeds; the Mastiff is a British original.

Breed sets the odds. The parents set the dog. Every number here shows its source, its spread and how sure we are. Nothing on this page is a prediction about one dog.

9YRMedian lifespan8.9 to 9.2, measured on real dogs.
0INHeightdogs null, bitches null. An ideal from the standard, not a range.
120–230LBWeight, all linesbreed dogs 160 to 230 lb; breed bitches 120 to 170 lb.
1HRSExercise, every dayRKC: up to 1 hour per day. AKC breed page energy level 3 of 5. The constraint most homes get wrong.

The body

What the breed is built like. Registry standards give an ideal, not a range.

Height at the shoulder

dogs 30 in · bitches 27.5 in

Breed clubAKC breed standard, 1991

Floor only; low is the minimum, no maximum printed.

Weight

dogs 160 to 230 lb · bitches 120 to 170 lb

Breed clubAKC

Registry breed-page band, not a standard. Center left blank because no ideal is printed.

Coat

AKC: outer coat straight, coarse and of moderately short length; undercoat dense, short and close lying; no fringe on belly, tail or hind legs; long or wavy coat is a fault. Colours fawn, apricot or brindle, with a dark mask. UKC: short and close-lying, not too fine over shoulders, neck and back. FCI: short and close-lying but coarse over neck and shoulders

Breed clubAKC breed standard, 1991

Shedding

RKC: sheds (yes). AKC breed page: shedding level 3 of 5

Breed clubThe Royal Kennel Club

Heat tolerance

4 of 5 · AKC: outer coat straight, coarse and of moderately short length, undercoat dense, short and close lying. UKC: short and close-lying. FCI: short and close-lying, coarse over neck and shoulders

DerivedAKC breed standard, 1991

Derived from the coat description (4 = short dense). The breed is also short-muzzled and very large, which the coat rule does not capture; treat the figure as coat-only.

How long they live, and what they cost

Measured on real dogs, with the sample and the spread. Never a guess.

Median lifespan

9 years (8.9 to 9.2)

MeasuredMcMillan KM, 2024

Median age at death in a UK sample; a population figure, never a prediction for one dog. Registry page bands (the AKC header's life-expectancy range) are not medians and are not used here.

The dog at home

What the breed asks of a day. The first thing most homes get wrong.

Exercise need

RKC: up to 1 hour per day. AKC breed page energy level 3 of 5

Breed clubThe Royal Kennel Club

RKC band mapped: up to 1 hour = 60.

Exercise need

RKC: up to 1 hour per day (large house, large garden, country). AKC breed page: energy level 3 of 5, mental stimulation needs 3 of 5

Breed clubThe Royal Kennel Club

Energy

AKC breed page energy level 3 of 5; playfulness 3; trainability 3; barking level 1; drooling level 4 (AKC bands, 1 to 5)

Breed clubAKC

Grooming load

2 of 5 · RKC: grooming once a week; coat length short; sheds. AKC breed page: coat grooming frequency 1 of 5

Breed clubThe Royal Kennel Club

RKC band mapped: once a week = 2.

Grooming

RKC: once a week. AKC breed page: coat grooming frequency 1 of 5, shedding level 3 of 5, drooling level 4 of 5

Breed clubThe Royal Kennel Club

The work

What it was built to do in the field, and what a test or trial asks of it.

Role

RKC: the Mastiff (once the Old English Mastiff) was employed as a guard dog, a gamekeeper's dog and a hunter of wolves, and for bear and bull baiting; the pits were outlawed in 1835. UKC: a long history as a fighting dog, protector of the home, and use against other animals and as a weapon in war; in America now a devoted family pet that may serve as a protector mainly by its imposing size. FCI utilization: watch and security dog. AKC standard temperament: grandeur and good nature, courage and docility; dignity rather than gaiety. AKC history feature: modern DNA research shows no single prototype mastiff spawned all heavy-boned breeds; the Mastiff is a British original

Breed clubThe Royal Kennel Club

Guard and watch breed, not a gun dog. The AKC history feature is editorial.

Field trial standard

None: FCI classes the Mastiff 'without working trial'

Breed clubFederation Cynologique Internationale

How common the problems are

Evaluated dogs skew toward breeding stock; the numbers are still the best there are.

Hip dysplasia

20.3% · 20.3% dysplastic of 14,037 OFA hip evaluations on record (current all-data, accessed Oct 9 2026); 76.8% normal; mild 14.2%, moderate 5.4%, severe 0.7%; breed rank 52 of the breeds listed

MeasuredOrthopedic Foundation for Animals

Voluntary registry: affected dogs are under-reported and evaluated dogs skew toward breeding stock, so true prevalence is likely higher. Rank 1 = highest dysplasia rate among the breeds listed.

Elbow dysplasia

15.5% · 15.5% abnormal of 8,716 OFA elbow evaluations on record (current all-data, accessed Oct 9 2026); 84.2% normal; grade 1 10.4%, grade 2 3.6%, grade 3 1.5%; breed rank 32 of the breeds listed

MeasuredOrthopedic Foundation for Animals

Voluntary registry: affected dogs are under-reported and evaluated dogs skew toward breeding stock, so true prevalence is likely higher. Rank 1 = highest dysplasia rate among the breeds listed.

More

akc bands

AKC breed page trait scores (1-5): Energy Level 3; Mental Stimulation Needs 3; Trainability Level 3; Barking Level 1; Watchdog/Protective Nature 5; Good With Young Children 5; Openness To Strangers 3; Good With Other Dogs 3; Shedding Level 3; Coat Grooming Frequency 1; Drooling Level 4; Affectionate With Family 5; Playfulness Level 3; Adaptability Level 4.

Breed clubAKC

Fourteen AKC bands in one row; the selector reads each by name. Breed-club ratings: a tendency, never a measurement.

What to ask a breeder for

The health clearances the breed’s own club and registry name. Reference only: what to ask for, never a statement about any dog’s health.

How to read this page

Every value carries a label. Measured means peer-reviewed data on many dogs. Studied means peer-reviewed, smaller or indirect. Breed club means a club or registry states it. Editorial means expert opinion with no measurement behind it. Where two good sources disagree, both are shown and neither is averaged.

Published when the entry rests on the best information available from no fewer than three independent sources, checked by a second pass that did not write it. 7 sources on this page. Found something wrong? Tell us and the correction is logged with its date.

Also called
English Mastiff, Old English Mastiff

Every breed, read the same way.

The breed index grows as entries clear the standard. Gun dogs first.

All published breeds

Your mastiff, on the record.

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