Alot people think that to know the "human" age of a dog, you just have to multiply its age by 7, well ... that's just wrong!
Practically, there is no mathematical formula (well at least, not a simple one) because the age of a dog does not follow a linear curve compared with the human age. Like many animals, "childhood" and "adolescence" occur much faster than humans. Indeed, the first year the dog grows five times faster than humans!
So it's rather from observations of the ages of dogs that veterinarians have established a correlation table (age chart) to see an equivalence in human age:
|Real dog age||1||2||3||4||5||6||7||8||9||10||11||12||13||14||15||16||17||18|
|Small dog age||20||28||32||36||40||44||48||52||56||60||64||68||72||76||80||84||88||94|
|Big dog age||16||22||31||40||49||58||67||76||85||96||105|
Small dog = dog under 15kg, Average dog = dog from 15 to 45 kg, Big dog = dog over 45 kg
Finally, the more a dog is big (from is breed), the more its youth will be slow, but it would then get old more quickly, and its life would be shorter.
Life expectancy of the dog:a dog can live 10 to 15 years depending on his size (and his breed).
If humans had Jeanne Calment, the oldest dog in the world would have been a dog named Bella.
She died in 2008 in Clay Cross (United Kingdom) at the age of 29 years, which would correspond to a human aged nearly 202 years !!!
Unfortunately, the age of the poor dog has not been formalized in the Guinness Book of Records, as his master had no document indicating his birth ...