Puppy Weight Calculator — Predict Adult Dog Weight

Predict your puppy's adult weight from current age and weight using size-category growth curves for toy, medium, large, and giant breeds.

July 2, 2026

Estimated Adult Size Category

Not sure? Check the breed standard for your puppy's breed, or use the parents' size as a guide for mixed breeds.

Current Age

Current Weight (lb)

Predicted Adult Weight

24.2 lb

At 12 weeks old, medium puppies are estimated at roughly 33% of adult weight.

Est. % of Adult Weight Now

33%

Expected Maturity

~12–14 months

This is a statistical estimate based on typical growth curves for the selected size category — actual adult weight depends heavily on genetics, breed, nutrition, and individual variation, and can differ meaningfully from this prediction. Estimates for giant breeds and very young puppies carry more uncertainty since more growth remains ahead of them. For a breed-specific estimate, check your breed's standard or ask your veterinarian.

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Reference Values

Last verified: Jul 2, 2026

Category	Range	What It Means	Status
Toy / Small (adult under 25 lb) ★	Mature by ~10–11 months	Fastest-maturing size category — reaches close to full adult weight by around 9–11 months, then growth essentially stops.	★ Best
Medium (adult 25–50 lb)	Mature by ~12–14 months	Reaches adult height around 10–12 months but continues filling out (chest, muscle) for another 1–2 months after that.	Good
Large (adult 50–90 lb)	Mature by ~15–18 months	Growth plates stay open longer — noticeable growth can continue well past a year old.	Okay
Giant (adult over 90 lb)	Mature by ~18–24 months	Slowest-maturing category. Breeds like Great Danes and Mastiffs may still be visibly filling out at 18+ months.	Poor

Source: General veterinary growth-curve guidance (breed size maturation timelines widely published by veterinary nutrition sources including Royal Canin Academy and Purina Institute puppy growth research)

Worked Examples

Toy/Small Puppy — 8 weeks, 3 lb

Size Category: Toy/Small
Age: 8 weeks
Current Weight: 3 lb

Predicted adult weight: ~11.1 lb

At 8 weeks, toy/small breeds are estimated at about 27% of adult weight: 3 ÷ 0.27 ≈ 11.1 lb. Small breeds mature fastest, reaching full size by ~10–11 months.

Medium Puppy — 12 weeks, 8 lb

Size Category: Medium
Age: 12 weeks
Current Weight: 8 lb

Predicted adult weight: ~24.2 lb

Medium breeds are estimated at about 33% of adult weight at 12 weeks: 8 ÷ 0.33 ≈ 24.2 lb.

Large Puppy — 16 weeks, 20 lb

Size Category: Large
Age: 16 weeks
Current Weight: 20 lb

Predicted adult weight: ~58.8 lb

Large breeds are estimated at about 34% of adult weight at 16 weeks: 20 ÷ 0.34 ≈ 58.8 lb. Growth continues well past a year for this size category.

Giant Puppy — 24 weeks, 45 lb

Size Category: Giant
Age: 24 weeks
Current Weight: 45 lb

Predicted adult weight: ~107.1 lb

Giant breeds are estimated at about 42% of adult weight at 24 weeks: 45 ÷ 0.42 ≈ 107.1 lb. Giant breeds keep growing until 18–24 months, so this estimate has wider uncertainty than smaller categories.

How to Use This Calculator

1

Select your puppy's estimated adult size category

Choose toy/small, medium, large, or giant based on breed standard, parent size, or a vet's estimate.
2

Enter current age

Enter age in weeks or months — more accurate for puppies at least 8 weeks old.
3

Enter current weight

Enter current weight in pounds from a recent weigh-in.
4

Read the predicted adult weight

The result shows predicted adult weight, current percentage of that weight, and typical maturity age for the selected size category.

What Each Value Means

Predicted Adult Weight (lb): Current weight divided by the estimated percentage of adult weight typically reached at the puppy's current age and size category — current weight ÷ (percentage ÷ 100).
Percent of Adult Weight (percent (%)): The estimated share of eventual adult body weight a puppy has reached at its current age, based on typical growth curves for its size category. Smaller breeds reach a higher percentage earlier; larger breeds take longer to reach the same percentage.

Frequently Asked Questions

How accurate is a puppy weight calculator?

Puppy weight predictions are statistical estimates, not guarantees — genetics, breed, nutrition, spay/neuter timing, and individual variation all affect final adult weight. Predictions made from younger puppies (under 12 weeks) or for giant breeds carry more uncertainty because more growth remains ahead of them. A prediction made at 6 months is generally more reliable than one made at 8 weeks.

What size category should I choose for a mixed-breed puppy?

For mixed breeds, the best estimate usually comes from knowing the size of one or both parents, if available. If parentage is unknown, paw size relative to leg/body proportions, breed guesses from a DNA test, and litter size can offer clues, but these are rougher indicators. When in doubt, a veterinarian who has examined the puppy's frame and growth plates can often give a more informed size-category estimate than owner guesswork alone.

At what age is a puppy weight prediction most reliable?

Predictions become more reliable as a puppy ages, since more of the growth curve has already played out. Estimates made after 4–6 months are generally more trustworthy than estimates made at 8 weeks, especially for large and giant breeds that continue growing well past a year old.

How long do different size dogs keep growing?

Toy and small breeds typically reach adult weight by 9–11 months. Medium breeds finish around 12–14 months. Large breeds can continue growing until 15–18 months. Giant breeds — such as Great Danes, Mastiffs, and Saint Bernards — often keep gaining weight until 18–24 months old.

Why do small breed puppies seem to grow faster than large breed puppies?

Small breeds have a shorter total growth window and reach a smaller target adult weight, so their growth curve compresses into fewer months. Large and giant breeds have a much bigger total weight gain ahead of them and their growth plates stay open longer, spreading that growth over a longer timeline — which is also why oversupplementing large-breed puppies with calories/calcium during rapid growth phases carries orthopedic risk and is worth discussing with a vet.