How big will my puppy get?
Enter your puppy's age, weight and size group to estimate its adult weight. The calculator uses growth curves measured in a published study of 173 puppies from 12 breeds.
- Share of adult weight now
- 56%
- In the other unit
- Near full size by about
Growth curve for your puppy
The line is the average growth curve of the size group. The dot is your puppy today, and the dashed line is the estimated adult weight.
Puppy growth chart by size
Share of adult weight a puppy has reached at each age, from the fitted growth curves in the study.
| Age | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 8 weeks (1.8 months) | 39% | 23% | 24% | 19% | 16% |
| 12 weeks (2.8 months) | 53% | 36% | 39% | 29% | 24% |
| 16 weeks (3.7 months) | 68% | 52% | 56% | 41% | 36% |
| 20 weeks (4.6 months) | 79% | 68% | 72% | 55% | 50% |
| 24 weeks (5.5 months) | 87% | 80% | 84% | 68% | 63% |
| 32 weeks (7.4 months) | 96% | 94% | 96% | 86% | 84% |
| 40 weeks (9.2 months) | 99% | 98% | 99% | 95% | 94% |
| 52 weeks (12.0 months) | 100% | 100% | 100% | 99% | 99% |
| 78 weeks (18.0 months) | 100% | 100% | 100% | 100% | 100% |
How the estimate works
In this formula age is in weeks, x0 is the age at which a puppy reaches half of its adult weight, and b is 100 divided by the early growth rate in percent per week. Puppies do not grow at a steady pace. They gain fastest early on and slow down as they near adult size, so a simple rule such as weight divided by age in weeks is least accurate for large breeds.
The calculator uses the average x0 and growth rate of the breeds in your size group. Where the study measured more than one breed in the group, the range shows the lowest and highest result among those breeds.
| Group | Breeds in the study | Adult weight (kg) | Half adult weight at (weeks) | 99% of adult weight at (weeks) |
|---|---|---|---|---|
| Toy | Papillon | 2.2 | 11.1 | 42 |
| Small | Cocker Spaniel, Miniature Schnauzer, Cairn Terrier | 6.3 to 10.2 | 14.1 to 16.6 | 41 to 47 |
| Medium | Beagle, English Springer Spaniel | 14.8 to 17.4 | 14.3 to 14.8 | 39 to 42 |
| Large | Labrador Retriever | 28.1 | 18.6 | 52 |
| Giant | English Mastiff, St. Bernard, Irish Wolfhound, Great Dane, Newfoundland | 43.3 to 66.9 | 18.1 to 22.9 | 46 to 65 |
When do puppies stop growing?
In the study, toy, small and medium breeds reached 99 percent of their adult weight at about 9 to 10 months. Large and giant breeds reached it at about 11 to 15 months.
Limits of this estimate
The data come from 173 puppies of 12 breeds raised in one research colony and fed commercial puppy diets. The toy and large groups each rest on a single breed, the Papillon and the Labrador Retriever, so treat those results with extra care. Individual dogs can differ a lot, and mixed breeds are harder to predict. The authors note that males may take longer than females to reach adulthood. Use the result as a guide and ask your vet about your own puppy.
Questions
How accurate is a puppy weight calculator?
It is an estimate. The curves describe the average of the breeds measured, and your puppy may grow faster or slower. The estimate is usually more reliable for puppies older than about four months than for very young ones.
How much should I feed a growing puppy?
Use the how much to feed a dog calculator and pick a puppy life stage. Check your puppy's weight against its growth every few weeks.
What if my puppy is a mixed breed?
Choose the size group that matches the adult size you expect, based on the parents or your vet's advice. The range under the result helps show how much the answer can vary.
Does the sex of the puppy matter?
It can. The study did not split results by sex, but the authors note earlier studies where males took longer to reach adulthood than females.
What if my puppy is already over a year old?
Most small and medium dogs are close to adult weight by about 10 months, and large and giant dogs by about 15 months. The calculator will show that your puppy is at or near full size.
Sources
- Hawthorne A.J., Booles D., Nugent P.A., Gettinby G., Wilkinson J. (2004). Body-Weight Changes during Growth in Puppies of Different Breeds. Journal of Nutrition 134(8 Suppl): 2027S to 2030S. doi:10.1093/jn/134.8.2027S. The symposium that published it was sponsored by the WALTHAM Centre for Pet Nutrition.
Last reviewed 2026-10-26. This page is general information and not veterinary advice.