English Mastiff weight chart by age
In a published growth study, adult English Mastiff dogs averaged about 147 lb (66.9 kg). Puppies reached 99 percent of that weight at around 65 weeks, which is about 15 months. Use the chart to see what is typical at each age, or enter your puppy's weight for an estimate of the adult size.
Your puppy is at about 32% of its adult weight.
English Mastiff puppy weight by age
| Age | Pounds | Kilograms | Of adult weight |
|---|---|---|---|
| 8 weeks | 24.3 | 11.0 | 16% |
| 12 weeks | 34.5 | 15.6 | 23% |
| 16 weeks | 47.3 | 21.4 | 32% |
| 20 weeks | 62.2 | 28.2 | 42% |
| 24 weeks | 78.2 | 35.5 | 53% |
| 32 weeks | 107.6 | 48.8 | 73% |
| 40 weeks | 127.7 | 57.9 | 87% |
| 1 year | 141.6 | 64.2 | 96% |
| 15 months | 146.0 | 66.2 | 99% |
| 18 months | 147.1 | 66.7 | 100% |
| Adult average | 147.5 | 66.9 | 100% |
Values are calculated from the growth curve fitted to the English Mastiff puppies in the study. Males and females were not reported separately here, and individual dogs vary, so treat the numbers as a typical pattern, not a standard.
English Mastiff growth chart
The dot marks one year. After that, weight changes slowly.
How fast does a English Mastiff grow?
This breed is in the giant group in our puppy size calculator. Growth was half done at about 23 weeks, which is when the curve is steepest. A English Mastiff is usually close to its adult weight by 15 months, although the body can keep filling out afterward. For how much to feed along the way, see the puppy feeding chart.
Questions
How much should a English Mastiff puppy weigh at 8 weeks?
In the study a English Mastiff weighed about 24.3 lb (11.0 kg) at 8 weeks.
How much should a English Mastiff puppy weigh at 16 weeks?
About 47.3 lb (21.4 kg), which is roughly 32 percent of the adult weight.
How much does an adult English Mastiff weigh?
The adult dogs in the study averaged about 147 lb (66.9 kg). Breed standards and individual dogs differ.
When is a English Mastiff fully grown?
Around 65 weeks (15 months) for weight, according to the growth curve.
Is my English Mastiff overweight?
Weight alone cannot say. Use the body condition check to look at ribs and waist.
Other breeds
Papillon, Cocker Spaniel, Miniature Schnauzer, Cairn Terrier, Beagle, English Springer Spaniel, Labrador Retriever, St. Bernard, Irish Wolfhound, Great Dane, Newfoundland. See also the dog weight chart for all breeds side by side.
Sources
- Hawthorne A.J. et al., "Body-weight changes during growth in puppies of different breeds", Journal of Nutrition, 2004.
Last reviewed 2026-10-26. This page is general information and not veterinary advice.