Dog Size Calculator - Puppy Weight Predictor
Predict how big your puppy will get when fully grown. This dog size calculator uses multiple veterinary-validated formulas to estimate your puppy's adult weight and height based on current weight, age, breed size, and parent weights. Get accurate predictions for small, medium, large, and giant breed dogs.
Calculate Your Puppy's Adult Size
Breed Size Category
Select the size category your puppy will fall into as an adult
Puppy's Current Information
4-52 weeks (1-12 months)
Parent Weights (Optional - Improves Accuracy)
Knowing parent weights provides more accurate predictions, especially for mixed breeds
How Puppy Size Predictions Work
Prediction Formulas by Method
1. Standard Growth Formula (52-Week Method):
\( \text{Adult Weight} = \frac{\text{Current Weight (lbs)}}{\text{Age (weeks)}} \times 52 \)
This formula assumes dogs reach adult size at 52 weeks (1 year). Most accurate for medium breeds. Example: A 15 lb puppy at 12 weeks = (15/12) × 52 = 65 lbs.
2. Breed-Specific Growth Multipliers:
\( \text{Toy/Small: Adult Weight} = \text{Weight at 8 weeks} \times 3 \)
\( \text{Medium/Large: Adult Weight} = \text{Weight at 16 weeks} \times 2 \)
Different breeds mature at different rates. Small breeds reach adult size faster (6-8 months), giant breeds slower (18-24 months).
3. Four-Month Doubling Method:
\( \text{Adult Weight} = \text{Weight at 16 weeks} \times 2 \)
Veterinarians commonly use this rule: puppies are roughly half their adult weight at 4 months (16 weeks). Simple but effective for most breeds.
4. Growth Percentage Method:
\( \text{Adult Weight} = \frac{\text{Current Weight}}{\text{Growth \% Completed}} \)
Uses breed-specific growth percentages by age. At 8 weeks: ~20% (toy), ~15% (large). At 16 weeks: ~50% (small), ~40% (large).
5. Parent Average Method:
\( \text{Adult Weight} = \frac{\text{Father Weight} + \text{Mother Weight}}{2} \times \text{Gender Factor} \)
Most accurate for purebreds. Males typically 10-15% larger than females. Gender factor: Male ≈ 1.1, Female ≈ 0.9.
Puppy Growth Milestones by Breed Size
Percentages show approximate portion of adult weight achieved at each age milestone.
Dog Size Categories & Breed Examples
🐕 Toy (2-12 lbs)
Chihuahua, Pomeranian, Yorkshire Terrier, Maltese, Toy Poodle. Height: 6-11 inches. Reach adult size: 6-8 months.
🐕 Small (12-25 lbs)
Dachshund, Shih Tzu, Beagle, Boston Terrier, French Bulldog. Height: 10-17 inches. Reach adult size: 8-10 months.
🐕 Medium (25-55 lbs)
Cocker Spaniel, Border Collie, Bulldog, Australian Shepherd. Height: 17-25 inches. Reach adult size: 12-14 months.
🐕 Large (55-100 lbs)
Labrador Retriever, German Shepherd, Golden Retriever, Boxer. Height: 23-27 inches. Reach adult size: 15-18 months.
🐕 Giant (100+ lbs)
Great Dane, Mastiff, St. Bernard, Newfoundland, Irish Wolfhound. Height: 27-32+ inches. Reach adult size: 18-24 months.
Frequently Asked Questions
How accurate are puppy weight calculators?
Puppy weight calculators provide estimates with 80-90% accuracy for purebreds when current weight, age, and breed are known. Accuracy improves significantly when parent weights are included. Mixed breed predictions are less precise due to varied genetic influences. The most accurate method is DNA testing (like Wisdom Panel), which analyzes genetic markers to predict adult size. Standard formulas work best between 8-16 weeks of age.
At what age is a puppy half its adult weight?
Most puppies reach approximately half their adult weight at 16 weeks (4 months) of age, which is why the "double at 4 months" rule is widely used by veterinarians. However, this varies by breed size: toy breeds reach 50% around 12 weeks, small breeds at 14-16 weeks, medium breeds at 16 weeks, large breeds at 16-18 weeks, and giant breeds at 18-20 weeks. Growth rates slow significantly after reaching half adult weight.
How big will my mixed breed puppy get?
Mixed breed predictions are challenging but possible. If you know the parent breeds, average their typical adult weights. If parents' actual weights are known, average them and adjust 10% up for males or 10% down for females. Look at paw size relative to body - disproportionately large paws suggest more growth ahead. The 52-week formula (current weight ÷ age in weeks × 52) provides a baseline estimate. For best accuracy, consider DNA testing to identify breed composition and genetic size markers.
When do puppies stop growing?
Growth completion varies significantly by breed size. Toy and small breeds typically reach full size at 6-10 months. Medium breeds finish growing around 12-14 months. Large breeds continue until 15-18 months. Giant breeds don't reach full size until 18-24 months and may continue filling out until age 3. While height typically stops first, dogs continue gaining muscle mass and "filling out" for several months after reaching adult height. Males generally take slightly longer to mature than females.
Can puppy paw size predict adult size?
Paw size provides clues but isn't a precise predictor. Puppies with large paws relative to their body often grow into those paws, suggesting they'll be larger adults. However, this method is unreliable because paw growth isn't proportional to body growth - some breeds naturally have larger or smaller paws. Paw size works best as a confirming indicator alongside weight-based formulas, not as a standalone prediction method. It's more folklore than science.
What factors affect puppy growth?
Multiple factors influence growth: Genetics (breed and parent size) is primary. Nutrition quality and quantity significantly impact growth rate - overfeeding can cause too-rapid growth, while underfeeding stunts development. Health issues, parasites, or illness can slow growth. Spaying/neutering before maturity may result in slightly taller dogs due to delayed growth plate closure. Exercise and activity level affect muscle development. Puppies from larger litters may be smaller at birth but catch up by 8-12 weeks.