Dogs are generally fully grown between 6 and 24 months, depending largely on their breed and size. Small dog breeds often reach full maturity by about 6 to 12 months, while medium breeds typically finish growing around 12 to 15 months. Large and giant breeds can take much longer, often between 18 to 24 months to be fully grown, as their bones and growth plates take more time to close.
Growth plates in the bones close at the end of a dog’s growing period, marking the end of height and skeletal growth, though muscle development may continue slightly beyond that. Smaller breeds reach this point sooner, whereas larger breeds take more time due to their size.
Here is a general timeline by breed size:
Breed Size| Typical Age Fully Grown
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Small| 6 - 12 months
Medium| 12 - 15 months
Large| 18 - 24 months
Giant| Up to 24 months
Overall, most dogs reach adult size by about 1 to 1.5 years, but for very large or giant breeds, it may take up to 2 years.