How big does a English Mastiff get?

Adult English Mastiff — Photo — Pleple2000, CC BY-SA 3.0 · Wikimedia Commons

A full-grown English Mastiff is a giant dog, weighing about 120–230 lb as an adult.

Adult weight: 120–230 lb
Also in kilograms: 54.4–104.3 kg
Size class: Giant

As a giant breed, a English Mastiff keeps growing for longer than a small dog — larger breeds reach their adult weight months later (Hawthorne et al., 2004). Expect steady growth well past the first year.

Compare every breed’s adult weight·Your dog’s age in human years

Weight varies within the English Mastiff by sex, genetics and health, and mixed-breed dogs fall between their parents. This is a typical range, not a guarantee.

Verified on July 28, 2026. Based on Wikidata — dog breed mass (property P2067) (Wikimedia Foundation, query run 2026-07-22, CC0 license), Wikidata — cat breed mass (property P2067) (Wikimedia Foundation, query run 2026-07-28, CC0 license) and Body-Weight Changes during Growth in Puppies of Different Breeds (Hawthorne et al., Journal of Nutrition, 2004, vol. 134, p. 2027S). See the method.