Dog Age Calculator: Dog Years to Human Years (by Size)

How dog years really work

The familiar idea that one dog year equals seven human years is a myth. Dogs grow up much faster at the start of their lives, then age at a rate that depends on their size. A one-year-old dog is roughly a 15-year-old human, and by two it is closer to a young adult of 24. From there, a small terrier ages gently while a giant breed such as a Great Dane ages quickly.

Dog age chart (human years by size)

Dog age	small	medium	large	giant
1 year	15	15	15	15
2 years	24	24	24	24
3 years	28	29	30	31
5 years	36	39	42	45
7 years	44	49	54	59
9 years	52	59	66	73
11 years	60	69	78	87
13 years	68	79	90	101
15 years	76	89	102	115

Figures are estimates based on the AKC/AAHA size-adjusted model. Individual dogs vary; always consult your vet for health guidance.

Frequently asked questions

How old is my dog in human years?

A dog reaches roughly 15 human years by its first birthday and about 24 by its second. After that, each dog year adds 4 to 7 human years depending on size: around 4 for small breeds, 5 for medium, 6 for large and 7 for giant breeds.

Is the "multiply by 7" rule accurate?

No. The ×7 rule is a myth. Dogs mature far faster in their first two years, and large breeds age more quickly than small ones later in life. A size-adjusted calculation is much closer to reality.

Why do bigger dogs age faster?

Larger breeds grow faster and have shorter lifespans, so each calendar year represents more biological ageing. A giant breed at 8 is comparable to a small breed at 11 or 12 in human terms.

When is a dog considered senior?

Most dogs enter their senior stage at around 70% of their expected lifespan: roughly 6 to 7 years for giant breeds, 8 to 9 for large, and 10 or more for small breeds. Twice-yearly vet checks are recommended from this point.

Curious how big your dog will get? Try our breed guides for adult weight, lifespan and temperament by breed.