Dog Age Calculator

Why not just multiply by 7?

The “one dog year equals seven human years” idea is a myth. Dogs reach adulthood within their first two years, and after that the pace depends on size: small dogs tend to age more slowly than large and giant breeds.

The rule of thumb vets use

The American Kennel Club, citing the American Veterinary Medical Association, describes it like this: the first year of a medium-sized dog's life equals about 15 human years, the second year adds about 9 more, and each year after that adds about 5. Size-based versions of this rule, which the calculator uses, add about 4 human years per year for small dogs, 5 for medium, 6 for large and 7 for giant breeds after age two.

The DNA-based formula

In 2020, researchers at the University of California San Diego compared age-related chemical changes in the DNA of dogs and people. From a study of Labrador retrievers, they proposed: human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. It only makes sense from about one year of age, and it was built on a single breed, so the calculator shows it as a second opinion.

Dog years to human years chart

Dog age	Small	Medium	Large	Giant	DNA formula
1 year	15	15	15	15	31
2 years	24	24	24	24	42
3 years	28	29	30	31	49
4 years	32	34	36	38	53
5 years	36	39	42	45	57
6 years	40	44	48	52	60
7 years	44	49	54	59	62
8 years	48	54	60	66	64
9 years	52	59	66	73	66
10 years	56	64	72	80	68
11 years	60	69	78	87	69
12 years	64	74	84	94	71
13 years	68	79	90	101	72
14 years	72	84	96	108	73
15 years	76	89	102	115	74
16 years	80	94	108	122	75

Sources: American Kennel Club, “How to Calculate Dog Years to Human Years”; UC San Diego on Wang et al., Cell Systems (2020), doi:10.1016/j.cels.2020.06.006.

Frequently asked questions

Is one dog year really seven human years?

No. Dogs grow up fast: by the rule of thumb vets use, a 1-year-old dog is like a 15-year-old person and a 2-year-old like a 24-year-old. After that, dogs age more slowly, at a pace that depends on size.

Why do big dogs age faster?

Large and giant breeds tend to have shorter lives than small breeds, so after their first couple of years each calendar year counts for more. That's why the calculator asks for your dog's size.

How old is a 10-year-old dog in human years?

By the rule of thumb, about 56 for a small dog, 64 for a medium dog, 72 for a large dog and 80 for a giant breed. The DNA-based formula gives about 68.

Which method is more accurate?

Neither is exact for every dog. The rule of thumb accounts for size; the DNA-based formula comes from a study of Labrador retrievers. Your vet can tell you how your dog is aging.