How big will my puppy get?
Enter your puppy's breed, age and current weight. The estimate comes from a growth model calibrated against published breed charts — not a single rule of thumb applied to every dog.
| Age | Expected weight | Of adult size |
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How this calculator works
Most puppy calculators apply one rule — usually "double the weight at 16 weeks" — to every dog. That rule is roughly right for a medium breed and meaningfully wrong for everything else, because the halfway point moves later as adult size increases. A Chihuahua is half its adult weight at about 14 weeks; a Great Dane not until about 21.
This tool models growth as a continuous curve whose shape depends on how big the dog will end up, then combines two independent estimates:
- Your puppy's own trajectory. Its current weight divided by the fraction of adult weight expected at its age. This captures whether your particular puppy is running large or small for its breed.
- Breed adult weight. The sex-specific typical adult weight, drawn from measured population data where it exists and breed standards elsewhere.
The two are blended, with the trajectory carrying more weight as your puppy gets older and its growth pattern becomes informative. At eight weeks the breed average dominates; by six months your puppy's own curve does.
Read the full methodology, sources and known limitations →
Questions people ask
How accurate is a puppy size calculator?
Tested against published breed growth charts, this model lands within about 7% of the chart’s own adult weight on average. That sounds precise, but the charts themselves disagree with each other by 10–30% for the same breed, so treat the range as the real answer and the single number as its midpoint. Accuracy is best for purebred, healthy-weight puppies measured after 16 weeks.
At what age can you tell how big a puppy will be?
Sixteen weeks is the practical turning point. Before 12 weeks, a puppy has not yet established the growth trajectory that projections depend on, and estimates swing widely. By four months most dogs are between 40% and 60% of their adult weight, and the picture firms up quickly from there.
Do puppies double their weight at 16 weeks?
Roughly, for medium breeds — but the halfway point moves later as adult size increases. A toy breed reaches half its adult weight around 14 weeks, a medium breed around 17–18, a large breed around 19–20, and a giant breed around 21. Applying the same rule to every dog is where most simple calculators go wrong.
Does neutering change how big my dog gets?
Sex hormones trigger growth-plate closure, so neutering before those plates close can delay closure and leave the long bones very slightly longer — the opposite of the common belief that it stunts growth. The effect on final size is small: the largest study on the question, covering over three million dogs, found shifts of under one centile width and concluded separate growth curves were unnecessary. This calculator therefore applies no adjustment for it. The more important consideration is timing and joint health, which is a conversation for your vet.
How do I predict a mixed-breed puppy’s size?
Parent weights are the best predictor available without a DNA test. Average the two adult parent weights, and expect the puppy to land near that average — a puppy rarely finishes much heavier than its larger parent. If the parents are unknown, the growth curve alone still works, just with a much wider range. For deliberate crosses like doodles, the Poodle parent’s variety (toy, miniature or standard) usually sets the size class.
Why is my puppy heavier or lighter than the chart says?
Individual variation is normal, and a single measurement matters far less than the trend. Healthy puppies tend to stay on their own growth percentile over time. Research tracking dogs to age three found that consistently crossing upward through percentiles from around 26 weeks was a meaningful early signal of later weight problems — so if your puppy is steadily pulling away from the expected curve rather than just sitting slightly off it, that is worth raising with your vet.
This is not veterinary advice. The results above are statistical estimates for general information and education, not predictions about your individual dog. Actual adult size depends on genetics, nutrition, health and ordinary individual variation, and may fall outside the range shown.
Do not use these numbers for dosing. Never calculate medication, anaesthetic or feeding amounts from a predicted weight. Use your puppy's actual current weight, measured by your veterinarian. If your puppy is growing much faster or slower than expected, contact your vet.