English Mastiff Weight & Size
How big does an English Mastiff get?
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
English Mastiff Size
As a giant breed, an 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.
English Mastiff Growth Chart
What an English Mastiff puppy weighs week by week, from the growth curve FEDIAF publishes (Nutritional Guidelines 2025, Table VII-8a) for a dog whose expected adult weight is 79.3 kg. It is an average, not a target, and it is only valid from 8 weeks to one year — FEDIAF notes that growth patterns show a certain individual variability. Read a row as the middle of a spread.
| Age | Weight | % of adult weight |
|---|---|---|
| 8 weeks | 24 lb (10.9 kg) | 14% |
| 10 weeks | 38 lb (17.4 kg) | 22% |
| 12 weeks | 50 lb (22.7 kg) | 29% |
| 14 weeks | 60 lb (27.2 kg) | 34% |
| 16 weeks | 68 lb (31.0 kg) | 39% |
| 18 weeks | 76 lb (34.5 kg) | 43% |
| 20 weeks | 83 lb (37.5 kg) | 47% |
| 24 weeks | 94 lb (42.8 kg) | 54% |
| 28 weeks | 104 lb (47.3 kg) | 60% |
| 32 weeks | 113 lb (51.2 kg) | 64% |
| 36 weeks | 120 lb (54.6 kg) | 69% |
| 40 weeks | 127 lb (57.7 kg) | 73% |
| 44 weeks | 133 lb (60.4 kg) | 76% |
| 48 weeks | 139 lb (63.0 kg) | 79% |
| 52 weeks | 144 lb (65.3 kg) | 82% |
Common questions
How much does a full-grown English Mastiff weigh?
An English Mastiff weighs 120–230 lb (54.4–104.3 kg) as an adult. That range is the mass Wikidata publishes for the breed under a CC0 license, re-checked here every week — it is a typical weight across many adult dogs, not a target for one dog.
Is an English Mastiff a giant dog?
Yes — an English Mastiff counts as a giant breed, going by the middle of its adult weight range (54.4–104.3 kg). The cut-offs between small, medium, large and giant are a common veterinary convention rather than one official standard, so a breed near a boundary can be described either way elsewhere.
When does an English Mastiff stop growing?
Later than a small dog. Hawthorne et al. (2004) measured that larger breeds keep gaining weight for longer, so an English Mastiff is likely to fill out well past its first birthday. We don't publish a month-by-month figure, because no source gives one breed by breed — and an invented number would be worse than none.
Why is there a range instead of one weight?
Because the source publishes a range. Within any breed, weight varies with sex, genetics, build and health, and a mixed-breed dog usually falls between its parents' breeds. Narrowing 120–230 lb down to a single number would look more precise while being less true.
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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 . Based on Wikidata — dog breed mass (property P2067) (Wikimedia Foundation, query run 2026-07-22, CC0 license), Body-Weight Changes during Growth in Puppies of Different Breeds (Hawthorne et al., Journal of Nutrition, 2004, vol. 134, p. 2027S) and Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs (FEDIAF (European Pet Food Industry Federation), 2025 edition (growth curves Table VII-8a, growth energy VII-8b and VII-10)). See the method.