Puppy Growth & Adult Weight Calculator
Estimate your puppy's adult weight based on their current age and weight.
Calculate how big your puppy will get using breed size formulas.
Puppy growth prediction is based on the well-known formula that uses current weight and age to project adult size. The formula differs by breed size category because small, medium, large, and giant breeds grow at very different rates and reach adulthood at different ages.
General formula:
Adult Weight ≈ (Current Weight ÷ Current Age in Weeks) × 52
This works as a rough estimate but breed size matters significantly:
Small breeds (under 10 kg adult weight) — e.g. Chihuahua, Pomeranian, Toy Poodle:
- Reach 50% of adult weight at 8–10 weeks
- Formula: Adult Weight ≈ Current Weight ÷ Current Age (weeks) × 52
Medium breeds (10–25 kg) — e.g. Beagle, Border Collie, Cocker Spaniel:
- Reach 50% of adult weight at 12–14 weeks
- Reach adult size around 12 months
Large breeds (25–40 kg) — e.g. Labrador, Golden Retriever, Siberian Husky:
- Reach 50% of adult weight at 16–18 weeks
- Reach adult size around 14–16 months
Giant breeds (over 40 kg) — e.g. Great Dane, St. Bernard, Mastiff:
- Reach 50% of adult weight at 20–26 weeks
- Reach adult size at 18–24 months
More accurate method — using 16-week weight: For medium to large dogs, weigh at 16 weeks and multiply by 2. For giant breeds, multiply 16-week weight by 2.5–3.
Factors that affect adult size:
- Genetics: The single biggest factor. If you know the parent weights, average them for a rough estimate.
- Gender: Males are typically 10–20% heavier than females of the same breed.
- Nutrition: Underfeeding slows growth; overfeeding a large breed puppy can cause joint problems.
- Neutering age: Neutering before full growth can slightly increase adult height in some large breeds.
Growth plates and development: Puppy bones have soft growth plates at the ends that harden as they mature. Over-exercising a puppy on hard surfaces before growth plates close (around 12–18 months for large breeds) can cause lasting joint damage. Avoid forced running and jumping until your vet confirms it is safe.
Note: This calculator gives an estimate only. A DNA breed test or veterinary assessment will give the most accurate adult size prediction for mixed-breed dogs.