A puppy is usually full grown in height and close to adult weight sometime between about 8 months and 2 years old, depending mostly on their size and breed.

Quick Scoop: Main Answer

Here’s the simple rule of thumb by adult size:

  • Toy dogs (around 5–12 lb): usually full grown by about 8–12 months.
  • Small dogs (about 12–24 lb): roughly 9–12 months.
  • Medium dogs (about 24–50/60 lb): around 12–15 months.
  • Large dogs (about 50/60–100 lb): about 15–18 months.
  • Giant dogs (over 100 lb): can keep growing until about 18–24 months.

In all breeds, the growth plates in the bones “seal” when they’re done growing in height; after that they mainly fill out with muscle and body condition.

Mini Sections

1. What “full grown” really means

  • Physically, most puppies reach adult height earlier, then slowly gain muscle and body mass for several more months.
  • Many dogs are considered adults at about 1 year, but full physical size can take anywhere from about 6 to 24 months depending on breed and size.
  • Giant and very large breeds are the slowest to mature and can still be filling out well into their second year.

Think of it like a teenager who suddenly gets tall, then spends another year or two filling out their frame.

2. General timelines by size

You can use these as a rough guide (individual dogs vary):

  • Toy/small breeds: rapid growth in the first 4–5 months, often near full size around their first birthday.
  • Medium breeds: grow fast for about 6 months, reach height around 9–12 months, then fill out by 12–15 months.
  • Large breeds: reach much of their height by about 12 months, with chest and muscle filling in up to 15–18 months.
  • Giant breeds: can keep gaining height and bulk until 18–24 months.

3. How to tell your puppy is close to full size

While every pup is different, these are common signs that they’re nearing adult size:

  • Adult teeth: by around 6 months most dogs have their full set of 42 adult teeth, which tends to happen before they reach full body size but signals they’re moving out of the “baby” phase.
  • Stable weight and height: if measurements stay fairly steady over a couple of months, they’re likely close to full grown.
  • Proportions: paws and head that finally look “in proportion” to the body, especially in mixed breeds, often mean they’re near adult size.

4. Why the timing matters

Knowing when your puppy is full grown helps you:

  • Plan when to switch from puppy food to adult food (small breeds often closer to 9–12 months, large/giant breeds closer to 12–18 months, with your vet’s guidance).
  • Protect their joints by avoiding over-exercise and keeping them a healthy weight while growth plates are still open.
  • Set expectations for training and behavior, since mental and social maturity can lag behind physical growth, especially in large and giant breeds.

A common example: a Labrador might look adult-sized at 12 months but still be mentally very “puppy” and keep filling out until around 18 months.

TL;DR: Most puppies are full grown around 1 year if they’re small, 12–18 months if they’re medium/large, and up to about 2 years if they’re giant breeds.

Information gathered from public forums or data available on the internet and portrayed here.