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Dog Age Calculator
One dog year is not seven human years. Enter your dog’s age and size to convert it with the guideline published by the American Veterinary Medical Association: dogs mature very fast in their first two years, then age more steadily, with large dogs aging faster than small ones.
AVMA guideline, size-adjusted.
- By the 2019 DNA-methylation formula
- 56.8 years
- By the old “× 7” rule
- 35 years
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Formula
How to use it
- Enter your dog’s age in years and months.
- Choose your dog’s adult size.
- Read the age in human years.
- Compare it with the DNA-based formula and the old times-seven rule shown below.
Worked examples
A 5-year-old medium-sized dog
- Age in human years
- 39 years
- By the 2019 DNA-methylation formula
- 56.8 years
- By the old “× 7” rule
- 35 years
A 10-year-old large dog
- Age in human years
- 72 years
- By the 2019 DNA-methylation formula
- 67.8 years
A 6-month-old puppy
- Age in human years
- 7.5 years
A 12-year-old small dog
- Age in human years
- 64 years
Where the numbers come from
The AVMA’s general guideline is that the first year of a medium-sized dog’s life equals about 15 human years, the second year about nine more, and each year after that about five. A one-year-old dog is sexually mature and nearly full grown — much closer to a teenager than to a seven-year-old child.
The size adjustment used after year two — four human years per dog year for small dogs, five for medium, six for large and seven for giant breeds — is a common approximation of veterinary age charts. It reflects a well-established fact: large breeds age faster and have shorter lives than small ones.
The 2019 DNA-methylation study
Researchers at the University of California San Diego compared chemical marks on the DNA of 104 Labrador retrievers with those of humans and derived the formula human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. It was posted in 2019 and published in Cell Systems in 2020.
It gives higher ages for young dogs — a one-year-old comes out at 31 — and flattens out later. It is based on a single breed, so it is shown here as a second opinion rather than the main result.
An estimate, not a diagnosis
Any conversion is a rough guide to life stage. Breed, weight, diet and health matter more than the number. Your vet can tell you when your dog should move to senior check-ups — typically around seven for large breeds and later for small ones.
Questions people ask
How old is a 5-year-old dog in human years?
About 39 for a medium-sized dog: 15 for the first year, 9 for the second and 5 for each of the next three. A small dog would be about 36 and a giant breed about 45.
Is one dog year really seven human years?
No. The times-seven rule underestimates young dogs badly — a one-year-old dog is closer to 15 — and takes no account of size.
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.
Do small dogs live longer than big dogs?
Yes, on average. Small breeds commonly live into their mid-teens, while giant breeds often live only 7 to 10 years.