Puppy Weight Calculator: Adult Weight by Age and Size
See a realistic adult-weight range, not one number, from published size-class growth charts — plus roughly how much growing your puppy has left.
Estimated adult weight: –
About – of adult weight reached so far
Size class used: – (estimated from age and current weight, since you weren't sure)
How this estimate works
Smaller dogs reach their adult weight fast — most toy and small breeds are within 10% of adult weight by around 8–9 months — while large and giant breeds keep growing well into their second year. This calculator models that shape with a size-specific growth curve based on the pattern published in Salt et al. (2017, PLOS ONE) and the WALTHAM breed-size growth charts, then works backward from your puppy's current weight-for-age to estimate where its adult weight will land.
If you're not sure what size your puppy will be, the calculator compares your puppy's current weight against the expected weight-for-age of every size class and picks the closest match — it says so in the result.
The model behind this calculator: % of adult weight by age and size
Modelled values that follow the growth pattern published by Salt et al. (2017) — not figures copied from the study. Individual puppies vary.
| Age | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 8 wk | 50% | 36% | 27% | 17% | 12% |
| 12 wk | 67% | 54% | 43% | 30% | 22% |
| 16 wk | 78% | 66% | 56% | 42% | 33% |
| 20 wk | 84% | 75% | 66% | 52% | 42% |
| 26 wk | 89% | 82% | 75% | 64% | 54% |
| 39 wk | 95% | 91% | 86% | 78% | 71% |
| 1 yr | 97% | 94% | 91% | 86% | 80% |
| 1.5 yr | 98% | 97% | 96% | 93% | 89% |
Typical adult weight by size class
| Size class | Typical adult weight |
|---|---|
| Toy (adult 2–9 lb) | 2–9 lb |
| Small (adult 10–25 lb) | 10–25 lb |
| Medium (adult 26–50 lb) | 26–50 lb |
| Large (adult 51–90 lb) | 51–90 lb |
| Giant (adult 91–180 lb) | 91–180 lb |
Limitations
- This is a range from a modeled growth curve, not a measurement of your specific dog — mixed breeds and littermates can diverge a lot from the average.
- Genetics, nutrition, spay/neuter timing and health all shift adult weight; the estimate gets more reliable as your puppy gets older.
- Ask your vet if your puppy's weight gain suddenly stalls, drops, or jumps well outside the range shown here, or if you're unsure about their body condition.
Sources
- Growth standard charts for monitoring bodyweight in dogs of different sizes — PLOS ONE (Salt, Morris, Wilson, Lund & German, 2017) (September 23, 2026)
- Breed-size growth charts for puppies — WALTHAM Petcare Science Institute (September 23, 2026)