Dog Years to Human Years Calculator
Convert your dog’s age to human years, adjusted for size, with the method shown.
Human-year equivalent
34human years
Method: the first dog year counts as 15, the second adds 9, then each year adds 5 for this size. It converts a number; it says nothing about your dog's health.
Epigenetic estimate (adult dogs): about 53.2 human years, from 16 x ln(age) + 31, a DNA-methylation fit published in 2019-2020 on Labrador retrievers. One breed, so treat it as a curiosity.
How old is my dog in human years?
Enter your dog's age in years and months, pick a size class, and the calculator converts it with the rule most dog-age charts use. The first year of a dog's life counts as 15 human years. The second year adds 9, so a two-year-old comes out at 24. After that, each dog year adds a fixed number of human years that depends on size: 4 for a small dog, 5 for a medium one, 6 for a large one and 7 for a giant breed. Months count in proportion, so a small dog of two years and six months comes out at 26.
This is the common 15/9/then 4–7 per year rule. It replaces the old "multiply by seven" shortcut, which is a fair average for a middle-aged dog but gets young dogs and giant breeds wrong.
A few worked examples
- 1 year: 15 human years, for every size
- 2 years: 24 human years, for every size
- 5 years: 36 (small), 39 (medium), 42 (large), 45 (giant)
- 10 years: 56 (small), 64 (medium), 72 (large), 80 (giant)
The second estimate
For dogs of one year and older the calculator also shows a second figure from a different method. A 2019 study of Labrador retrievers compared DNA methylation, a chemical pattern on DNA that changes with age, in dogs and people, and proposed the formula human age = 16 × ln(dog age) + 31. It is a curve fitted to one breed, so treat it as a curiosity beside the size-adjusted rule, not a correction to it. The two methods often disagree by several years, which is the honest picture: there is no single exact conversion.
Choosing a size class
Use the size your dog is, or will be, as an adult, by weight: small, medium, large or giant. Larger dogs are generally thought to age faster in the later years, which is why the number of human years per dog year rises with size. If your dog is a mix, pick the class closest to its expected adult weight.
What the number is not
It is a conversion of a number, not an assessment of your dog. It is not a "health age", it does not say whether your dog is slowing down, and it cannot tell you when your dog counts as a senior. Those depend on the individual animal, and your vet is the right person to ask which check-ups suit your dog's age and size.
Questions and answers
How many dog years is one human year?
There is no fixed ratio. With the rule used here, a dog’s first year counts as 15 human years, the second as 9, and every later year as 4 to 7 depending on size. The old "one human year equals seven dog years" is only a rough average.
How old is a 3-year-old dog in human years?
About 28 for a small dog, 29 for a medium dog, 30 for a large dog and 31 for a giant breed, using the size-adjusted rule on this page.
How old is a 10-year-old dog in human years?
About 56 for a small dog, 64 for a medium dog, 72 for a large dog and 80 for a giant breed. The gap between sizes widens with every year after the second.
Is there a dog age calculator by breed?
This one uses size class, because that is how the common conversion rule works. The only breed-specific figure is the Labrador-based formula shown for dogs of one year and older, and it comes from a single study.
Does a dog’s human age tell me when it is a senior?
No. When a dog is treated as a senior varies with size and with the individual dog, so ask your vet what is reasonable for yours.
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