The "human" age of your dog depends on many factors including breed, weight, nutrition, and activity level. A puppy grows rapidly up to 18 months of age. In fact, most experts now estimate that first year of a dog's life is equal to approximately 15 human years.
Larger and giant breeds are generally considered ‘seniors’ by the time they reach five, while medium sized breeds are considered seniors at approximately seven. Small
and toy breeds live longer and reach seniority at around ten years
Here is a neat chart: