Dogs are generally considered adults between 1 and 2 years old, but the exact age depends a lot on their size and breed.

Quick Scoop

For most pet owners, a dog stops being a “puppy” and becomes an adult when:

  • They are roughly 1–2 years old.
  • Their bones are fully developed and they’ve reached their adult height and weight.
  • Their behavior has settled a bit and that wild puppy energy has started to level off.

By size: age ranges

Smaller dogs grow up faster, while big and giant breeds take longer to reach adulthood.

  • Extra-small / toy breeds (under about 10 lbs): often adult around 8–10 months.
  • Small breeds (up to ~20–25 lbs): usually considered adults around 9–12 months.
  • Medium breeds (about 25–55 lbs): around 12 months to reach adult status.
  • Large breeds (about 55–100 lbs): often 15–18+ months to be considered adult.
  • Giant breeds (over ~100 lbs): may not be fully adult until 18–24 months or even close to 3 years behaviorally.

Physical vs. emotional adulthood

Dogs don’t grow up “all at once”; different types of maturity arrive at slightly different times.

  • Physical maturity: when growth plates close and body size is basically final; this is the main marker used to switch from puppy to adult food.
  • Sexual maturity: often around 6–12 months, when they’re capable of breeding, but they are not truly adult in body or mind yet.
  • Emotional/behavioral maturity: can lag behind physical growth, sometimes not arriving until 18–36 months, especially in larger, high-energy breeds.

Practical “adult dog” signs

Many vets and trainers consider a dog functionally adult when several signs line up.

  • Growth has plateaued and weight/height have stabilized.
  • Puppy teeth are gone and adult teeth are fully in (usually by ~6 months, with continued maturing after).
  • Energy and impulsiveness are a bit calmer, and training “sticks” more reliably.
  • Other adult dogs start treating them less like a puppy and more like a peer.

Why it matters

Knowing when dogs are considered adults helps you make better choices for their care.

  • Food: time the switch from puppy to adult formula so they don’t get too many calories or too few nutrients while still growing.
  • Exercise: avoid over-stressing joints in big breeds before the growth plates close.
  • Training: expect that “teenage” phases between ~6–18 months can be bouncy and test boundaries even if they’re nearly adult-sized.

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