Bullmastiff

Pinschers & molossoids

Giant

Median 10.2 y

FCI group 2 · Pinscher and Schnauzer, Molossoid and Swiss Mountain Dogs · Derived from the adult weight midpoint (50 kg)

Median survival across 3,357 UK dogs (VetCompass, McMillan 2024) · half live 7–12 y

The Bullmastiff is an English breed of dog of mastiff type and large size, with a solid build and a short muzzle. It was developed as a guard dog in the nineteenth century by cross-breeding the English Mastiff with the now-extinct Old English Bulldog. It was recognised as a breed by The Kennel Club in 1924.

Affectionate

Loyal

Brave

Summary from Wikipedia (CC BY-SA) · reference ranges from the Kintail breed dataset

Adult weight

Reference

Male

50–59 kg

Female

41–50 kg

The breed standard (The Kennel Club)

Two types. The AKC and the KC/FCI standards describe a different-sized Bullmastiff, so Kintail bands your dog against the one your region follows — set it in Settings. KC/FCI type: males 50–59 kg at 64–69 cm, females 41–50 kg at 61–66 cm. AKC type: males 49.9–59 kg at 63.5–68.6 cm, females 45.4–54.4 kg at 61–66 cm.

Weight for age

Stock data

Male

Female

Expected range

Expected range from the breed's own adult weight, kilograms. Growth reference: Hawthorne et al. 2004, WALTHAM (five giant-breed fits, n=35).

Heat cycles · females

Stock data

First heat

8–12 mo

typical

Interval

180 d

typical

Bleeding

~9 d

typical

Proestrus 9d

Estrus 9d

Diestrus 52d

Anestrus 110d

General figures for dogs, not for this breed — individual cycles vary widely.

Questions people ask

Adult males usually weigh 50–59 kg and females 41–50 kg. Most are close to their full size by around 13 months, though the last little bit of filling out takes longer. Growth reference: Hawthorne et al. 2004, WALTHAM (five giant-breed fits, n=35).

No Bullmastiff cycle figures are published here yet, so this is general guidance rather than a breed number: 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.

The median is 10.2 y. Median survival across 3,357 UK dogs (VetCompass, McMillan 2024) · half live 7–12 y. How the later years go comes down to weight, teeth, exercise and regular check-ups far more than to the breed.