A puppy is generally considered fully grown by the time its bones and joints have finished developing, which varies by breed size:

• Extra small breeds (<8 lbs): fully grown by about 9-11 months.
• Small breeds (8-20 lbs): around 12 months.
• Medium breeds (21-50 lbs): around 12-15 months.
• Large breeds (51-130 lbs): between 15-24 months.
• Giant breeds (>130 lbs): up to 24 months or 2 years.

Small breed puppies mature more quickly, often reaching full size by 6 to 8 months. Medium breeds typically stop growing at about 12 months. Larger and giant breeds take longer, sometimes up to 18-24 months to reach their full adult size because their bigger bones need more time to grow. After their growth plates close, bones stop growing, marking the end of height growth, though muscle and fat development may continue.

So, the time for a puppy to be fully grown ranges from about 6 months for the smallest breeds to up to 2 years for the largest breeds.