Free Tool
Puppy Age Calculator
How old is your puppy in weeks?
Track their development stage and what to do at each milestone — from newborn to one year.
Please choose a valid birth date.
Development Stages, Week by Week
Neonatal (0–2 weeks)
Eyes and ears closed; relies entirely on mom · Sleeps about 90% of the time · Cannot regulate body temperature on its own
Transitional (2–4 weeks)
Eyes and ears open · First teeth begin to appear · Starts standing, walking and exploring the whelping box
Socialization window (4–12 weeks)
Critical socialization period — safely expose to new people, sounds and surfaces · Weaning onto solid puppy food begins around 3–4 weeks · First vaccinations typically start at 6–8 weeks · Best age to go to a new home is 8 weeks or later
Juvenile (3–6 months)
Losing baby teeth; adult teeth coming in · Vaccine booster series continues (10–16 weeks) · Good age to start basic obedience training · Rapid growth phase — most weight gain happens now
Adolescent (6–12 months)
Sexual maturity begins; discuss spay/neuter timing with your vet · Adult teeth fully in · Energy and testing boundaries — consistent training matters most now · Switch from puppy food toward adult food nears (breed-size dependent)
Young Adult (12+ months)
Most small/medium breeds are physically mature · Large breeds may continue filling out until 18–24 months · Move to annual wellness exams
The Socialization Window (4–12 Weeks)
This is the single most important stretch of a puppy's development. Their brain is primed to form positive associations with new people, animals, sounds and environments. Well-socialized exposure during this window (done safely, ideally alongside your vet's vaccine guidance) has a lasting effect on confidence and behavior for the rest of their life.
Milestones are general guidelines and vary by breed and individual puppy. Talk to your veterinarian about your puppy's specific development and vaccine schedule.
Frequently Asked Questions
How old is my puppy in weeks?
Enter your puppy's birth date above and we'll calculate their exact age in weeks and show their current development stage.
What milestones should my puppy hit?
Eyes and ears open around 2 weeks, first teeth appear around 3–4 weeks, the critical socialization window runs from about 4–12 weeks, and adult teeth come in by 6–7 months.
When can I start training my puppy?
You can start gentle basic training (name recognition, sit, simple cues) as early as 8 weeks. The 4–12 week socialization window is the single best time to safely introduce new people, sounds and experiences.