When do Mastiffs stop growing?
As a giant breed, Mastiffs usually reach their adult weight at around 18-24 months, and are typically about half their adult weight by around 6 months. They may keep filling out (gaining muscle and chest depth) for a few months after their height stops increasing.
Feeding a growing Mastiff
- Feed a complete puppy food formulated for large-breed puppies, which controls calcium and calories to support healthy bone growth.
- Split food into 3-4 meals a day until about 6 months, then 2 meals.
- Keep your puppy lean. You should be able to feel the ribs easily. Use the dog food calculator (puppy setting) as a starting point.
- Weigh your puppy every 1-2 weeks and compare with the chart above.
Is my Mastiff puppy overweight or underweight?
A puppy slightly outside the chart range is usually fine if it is active, eating well and has a good body shape. Talk to your vet if your puppy is far outside the range, stops gaining weight, or looks pot-bellied or bony. Parents' size is a strong clue: puppies from smaller parents often finish at the lower end.
Other breed growth charts
- Rottweiler80-135 lb
- Great Dane110-175 lb
- Cane Corso88-110 lb
- Bernese Mountain Dog70-115 lb
- Newfoundland100-150 lb
- Saint Bernard120-180 lb
- Great Pyrenees85-160 lb
- Akita70-130 lb
Frequently asked questions
How big will my Mastiff get?
Most adult Mastiffs weigh 120-230 lb. Enter your puppy's weight and age in the calculator above for a personalized estimate.
How much should a 6-month-old Mastiff weigh?
Typically about 66-127 lb, depending on sex and genetics.
At what age is a Mastiff full grown?
Usually around 18-24 months.