Find the dog’s birth date
Subtract the birth date from today’s date
Convert the result into years, months, and days
If the birth date is unknown, estimate age by teeth, size, coat, eyes, and activity level
Use the common estimate that the first dog year is about 15 human years
Use the common estimate that the second dog year adds about 9 human years
Use the common estimate that each year after that adds about 5 human years
Adjust the estimate based on the dog’s size and breed
Small dogs often age more slowly than large dogs
Large dogs often age more quickly than small dogs