Compare Human Age to Dog Age

The common unit of measure to compare dog versus human age is:

1 human year = 7 dog years

Different breeds of dogs age at vastly different rates so this rule of thumb only goes so far. Giant dogs like Great Danes and St. Bernards may have a life expectancy of under 10 years. Chihuahuas might still be going strong at 15. You can think of some dogs as either aging faster or simply not living as long as others. In any case, a life that is significantly shorter than the average human life is one of the difficulties that dog lovers face.

Alternatives

Alternatively, since dogs reach maturity in about 1 year, that could be seen as 16 in human terms. Then add about 7, 5 or 4 years for every year your dog ages depending on the size of your dog.

Giant breeds examples: Great Danes, Mastiffs Large breeds: Retrievers, Collies Small breeds: Chihuahuas, Pomeranians

A 5 year old giant breed dog would then be: (5-1) x 7 +16 = 44 in human terms

A 5 year old large breed dog would then be: (5-1) x 5 + 16 = 36 in human terms

A 5 year old small breed dog would then be: (5-1) x 4 + 16 = 32 in human terms

Human equivalent years

Dog Years	Giant Breed	Large Breed	Small Breed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22	16 23 30 37 44 51 58 65 72 79 86 93 100	16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101	16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100

Specific breeds such as Border Collies and Bulldogs can have shorter life expectancies than their size would suggest. This could be because Border Collies lead hyper active lives and Bulldogs are essentially dwarfed Mastiffs and share the shorter lives of their ancestors. Beyond genetics, good nutrition, daily exercise, medical care, a warm family environment and an interesting life all serve to increase the lifespan of your dog. Note that the average lifespan of a dog in the US has doubled in the last several decades. The basic dog hasn’t changed as much but the care of dogs has changed dramatically for the better.