How big will your puppy get? It depends on the breed, and the answer determines everything — when to spay or neuter, how much to feed, and when growth plates close so you don't over-exercise a giant-breed pup.
How puppies grow
All puppies hit ~25% of their adult weight by 16 weeks, ~50% by 24 weeks, and ~75% by 6 months. After that, growth slows — large breeds continue until 18 months, giants until 24 months. The critical window for joint health is the first year: over-exercising a large-breed puppy can damage developing growth plates.
The breed-size growth chart
Use this to track expected weight at each age. Height is not a reliable predictor — weight is. Weigh weekly until 16 weeks, then monthly.
Tiny breeds (under 10 lb adult)
| Age | Typical weight | Fraction of adult |
|---|---|---|
| 8 weeks | 1.5–3 lb | ~25% |
| 12 weeks | 2.5–4.5 lb | ~40% |
| 16 weeks | 3.5–6 lb | ~55% |
| 24 weeks | 5–7.5 lb | ~75% |
| 6 months | 6–8.5 lb | ~90% |
| 12 months | Adult | 100% |
Small breeds (10–25 lb adult)
| Age | Typical weight | Fraction of adult |
|---|---|---|
| 8 weeks | 3–6 lb | ~25% |
| 12 weeks | 5–9 lb | ~40% |
| 16 weeks | 7–12 lb | ~55% |
| 24 weeks | 10–16 lb | ~75% |
| 6 months | 13–20 lb | ~90% |
| 9 months | Adult | 100% |
Medium breeds (25–50 lb adult)
| Age | Typical weight | Fraction of adult |
|---|---|---|
| 12 weeks | 8–15 lb | ~30% |
| 16 weeks | 12–20 lb | ~45% |
| 24 weeks | 18–30 lb | ~65% |
| 6 months | 22–37 lb | ~85% |
| 9 months | Adult | 100% |
Large breeds (50–100 lb adult)
| Age | Typical weight | Fraction of adult |
|---|---|---|
| 12 weeks | 15–25 lb | ~30% |
| 16 weeks | 22–35 lb | ~45% |
| 24 weeks | 32–50 lb | ~60% |
| 6 months | 40–62 lb | ~80% |
| 12 months | 48–75 lb | ~95% |
| 18 months | Adult | 100% |
Giant breeds (100+ lb adult)
| Age | Typical weight | Fraction of adult |
|---|---|---|
| 12 weeks | 20–35 lb | ~25% |
| 16 weeks | 30–45 lb | ~35% |
| 24 weeks | 45–65 lb | ~50% |
| 6 months | 55–80 lb | ~65% |
| 12 months | 70–100 lb | ~85% |
| 24 months | Adult | 100% |
When to spay or neuter
This used to be "6 months, no exceptions." New research shows timing matters by breed size:
| Breed size | Recommended age | Rationale |
|---|---|---|
| Tiny / small | 4–6 months | Done before first heat; minimal orthopedic risk |
| Medium | 6–9 months | Balanced — before first heat, low joint risk |
| Large | 12 months | Allows growth plates to close, reducing hip dysplasia risk |
| Giant | 18 months | Late sterilization reduces cancer risk without compromising growth |
Signs you're over- or under-feeding your pup
Feel your puppy's ribs: you should feel them with light pressure but not see them prominently. A visible "tuck" from ribs to hips is normal; a tucked abdomen (hiding the rib line) suggests underfeeding. Overfed pups develop a "corn cob" shape — wide at the ribs, narrow at the waist.
Breed-specific note: growth charts are averages. Individual genetics, neuter status, and activity level all shift the curve. A deviation of 10–15% from the chart is normal; more than that warrants a vet check.