What is 12 doggy years in humans years?

The dog is 54 years old in human life, an a dog ages 7 years per year to human life.

Actually, dogs "turn" 18 (in dog years) on their 1st (human years) birthday. For every year after (human), add five and you'll get your dog's age. So your dog is 18+5+5+5+5+5+5+5+5+5+5+5, which equals 73 in dog years.