Mastiff Growth Chart: How Big Will Yours Get?
The honest answer starts with the official standard: Mastiff adults run 120 to 230 lb per the AKC breed standard. Your puppy's own weight and age narrow that further.
| Male (AKC) | 160 to 230 lb |
|---|---|
| Female (AKC) | 120 to 170 lb |
| Size class | Giant |
A 16-week-old Mastiff weighing 70 lb comes out at 140 to 227.5 lb as an adult in our predictor — the same engine as the calculator, preset to this breed.
Run your own numbers in the puppy weight calculator — it combines this breed range with two published growth formulas and your puppy's current weight.
How giant dogs grow
Giant-breed puppies grow on a longer clock than smaller dogs. A toy-breed puppy typically reaches half its adult weight by around 12 weeks old, while a giant-breed puppy does not hit that halfway point until around 26 weeks, roughly twice as long. Giant breeds reach full adult size well into their second year, with a skeleton that stays immature until somewhere between 10 and 16 months old, later than the 8 to 12 months typical of small and medium dogs.
A single weight reading does not tell you much over a growth period this long. Vets track puppies against a growth curve, a range built from many dogs of similar size, and watch where a puppy sits on that curve across several checkups rather than judging one number alone. Sitting toward the high or low edge of that range is often just normal variation between dogs. When a puppy's spot on the curve shifts a lot between checkups, that's worth a chat with a vet, not a reason to worry on its own.
Why we don't publish a week-by-week weight table
Charted growth curves exist in veterinary research, but no source publishes the underlying week-by-week numbers in verifiable form — so we won't fake one. Our methodology page explains exactly what data this page uses and where it comes from. For tracking, weigh your puppy regularly and compare against the adult range above, or read what to track week by week.
Common questions
How big will a Mastiff get?
120 to 230 lb at maturity, per the AKC standard. Individual dogs can land outside the standard, especially mixes and outlier bloodlines.
Is my Mastiff puppy on track?
Enter their age and current weight in the weight predictor. If the formula estimate lands far outside the breed range, the tool flags it — that usually means tracking above or below standard, and it's worth mentioning at your next vet visit.
When do they stop growing?
Growth timing varies by size class more than by breed — our guide on when dogs stop growing covers what the research supports.
Estimates, not guarantees, and not veterinary advice. Sources for every number on this page: methodology.