Neapolitan Mastiff Weight, Size & Lifespan
How big does a Neapolitan Mastiff get?
A full-grown Neapolitan Mastiff is a giant dog, weighing about 110–150 lb as an adult.
- Adult weight
- 110–150 lb
- Also in kilograms
- 49.9–68 kg
- Size class
- Giant
- Life expectancy
- 7–9 years
Wikidata publishes 110–154 lb for this breed. The two sources don’t measure the same thing — see why.
Neapolitan Mastiff Size
As a giant breed, a Neapolitan 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.
Neapolitan Mastiff Lifespan
How long do Neapolitan Mastiffs live?
The American Kennel Club publishes a life expectancy of 7–9 years for the Neapolitan Mastiff, on its breed page. That is a figure for the breed, not a prediction for one dog — an individual Neapolitan Mastiff can fall on either side of it.
A second source measured it instead of publishing it. McMillan et al. (2024) followed 367 dogs of this breed in the United Kingdom and recorded 210 deaths, giving a median age at death of 9.3 years (95% CI 8.8–10.2 years).
⚠️ The two do not agree, and the gap is not small: 7–9 years against 9.3 years. We show both rather than averaging them, because they are not measuring the same thing. The AKC figure is what the breed club publishes for the breed; the McMillan figure is the age half of the dogs in that study had died by. A median at death sits below a life expectancy almost by construction — and here it lands above the published range, which is worth knowing either way.
Neapolitan Mastiff Growth Chart
What a Neapolitan 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 59.0 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 | 18 lb (8.1 kg) | 14% |
| 10 weeks | 28 lb (12.9 kg) | 22% |
| 12 weeks | 37 lb (16.9 kg) | 29% |
| 14 weeks | 44 lb (20.2 kg) | 34% |
| 16 weeks | 51 lb (23.1 kg) | 39% |
| 18 weeks | 56 lb (25.6 kg) | 43% |
| 20 weeks | 61 lb (27.9 kg) | 47% |
| 24 weeks | 70 lb (31.8 kg) | 54% |
| 28 weeks | 77 lb (35.1 kg) | 60% |
| 32 weeks | 84 lb (38.0 kg) | 64% |
| 36 weeks | 89 lb (40.6 kg) | 69% |
| 40 weeks | 94 lb (42.8 kg) | 73% |
| 44 weeks | 99 lb (44.9 kg) | 76% |
| 48 weeks | 103 lb (46.8 kg) | 79% |
| 52 weeks | 107 lb (48.5 kg) | 82% |
Common questions
How much does a full-grown Neapolitan Mastiff weigh?
A Neapolitan Mastiff weighs 110–150 lb (50–70 kg) as an adult. That range is the weight the American Kennel Club publishes in the breed's official standard, re-checked here every week — it is a typical weight across many adult dogs, not a target for one dog. Wikidata publishes 110–154 lb for the same breed — a breed standard and a set of measurements don't answer the same question, so this page names both rather than picking one.
Is a Neapolitan Mastiff a giant dog?
Yes — a Neapolitan Mastiff counts as a giant breed, going by the middle of its adult weight range (50–70 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 a Neapolitan Mastiff stop growing?
Later than a small dog. Hawthorne et al. (2004) measured that larger breeds keep gaining weight for longer, so a Neapolitan 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 110–150 lb down to a single number would look more precise while being less true.
How long do Neapolitan Mastiffs live?
The American Kennel Club publishes a life expectancy of 7–9 years for the breed, re-checked here every week. That is a figure for the breed, not a prediction for one dog: an individual Neapolitan Mastiff can fall on either side of it, and how a dog is fed, exercised and cared for moves the odds. A second source measured it rather than publishing it: McMillan et al. (2024) followed 367 dogs of this breed in the United Kingdom, recorded 210 deaths, and report a median age at death of 9.3 years (95% CI 8.8–10.2 years). The two disagree here — 7–9 years against 9.3 years — and we show both rather than averaging them, because they are not measuring the same thing.
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Weight varies within the Neapolitan 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), Breed weights — official AKC breed standards (American Kennel Club, breed pages, accessed 2026-07-29), Breed life expectancy — AKC breed pages (American Kennel Club, breed pages, accessed 2026-08-10), Longevity of companion dog breeds: those at risk from early death — Supplementary Table S3 (McMillan et al., Scientific Reports (2024), 14:531, 584,734 UK dogs — Kaplan-Meier median survival for 155 breeds), 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.