Dog age in human years calculator
The first year of a dog's life equals about 15 human years and the second about 9 more, so a 2 year old dog is about 24. After that, small dogs age about 4 human years per year and giant dogs about 7. Larger dogs reach their senior years sooner.
Sources checked 30 September 2026. How we check facts
Why "multiply by 7" is wrong
The old rule says one dog year equals seven human years. It is easy to remember, but it is not accurate. Dogs grow up much faster than people in their first two years, and then age at a rate that depends on their size.
This calculator uses the size-based model from the AKC and AVMA. The first dog year counts as 15 human years. The second counts as 9 more, which makes 24. After that, each dog year adds 4 human years for small dogs, 5 for medium dogs, 6 for large dogs and 7 for giant dogs. Bigger dogs age faster and live shorter lives on average.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 | 31 |
| 4 years | 32 | 34 | 36 | 38 |
| 5 years | 36 | 39 | 42 | 45 |
| 6 years | 40 | 44 | 48 | 52 |
| 8 years | 48 | 54 | 60 | 66 |
| 10 years | 56 | 64 | 72 | 80 |
| 12 years | 64 | 74 | 84 | 94 |
| 14 years | 72 | 84 | 96 | 108 |
| 16 years | 80 | 94 | 108 | 122 |
Toy dogs follow the small column.
Life stage matters more than the number. Puppies are still growing, adults are in their prime, and seniors need closer care. Senior dogs usually benefit from a vet check-up every 6 months.
Dog age questions
Is one dog year really 7 human years?
No. Dogs grow up much faster at the start. The first year equals about 15 human years and the second about 9 more. After that, the rate depends on size: about 4 human years per year for small dogs and up to 7 for giant breeds.
Why do big dogs age faster?
Large and giant breeds have shorter lifespans, so each year after the second counts for more human years. A 6 year old small dog is about 40 in human years, while a 6 year old giant dog is about 52.
When is a dog a senior?
Vets treat roughly the last quarter of a dog's expected lifespan as senior. That is about 11 years for small dogs, 10 for medium dogs, 8 for large dogs and 7 for giant dogs. Senior dogs usually need a vet check every 6 months.
What is the epigenetic dog age formula?
A 2020 study of DNA changes in 104 Labradors proposed human age = 16 x ln(dog age) + 31. It fits Labradors well but does not adjust for size, so we show it only as a second view.
When is my puppy an adult?
When it has finished growing. Toy and small dogs are adult at about 10 months, medium dogs at about 12 months, large dogs at about 15 months and giant dogs at about 18 months.
Sources
- How to Calculate Dog Years to Human Years. American Kennel Club. Accessed 30 September 2026.
- 2019 AAHA Canine Life Stage Guidelines. Journal of the American Animal Hospital Association. Accessed 30 September 2026.
- Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome (Wang et al.). Cell Systems. Accessed 30 September 2026.
- Senior pets. American Veterinary Medical Association. Accessed 30 September 2026.
Guides
-
Reading your pet's body condition score
The 1 to 9 body condition score explained: how to check your dog or cat at home in a minute, what the ideal 4 to 5 looks like, and why the trend matters most.
-
How much should my dog weigh?
Breed weight ranges are a starting point, not a verdict. Combine the scale, a body condition check and a monthly trend to know if your dog's weight is healthy.
-
How often does my dog need vaccines?
Adult dogs need the core vaccine every 3 years in the US, UK, Canada and Australia, and yearly in India. See rabies, lepto and kennel cough by country.
More from Maggie: Vaccine tracker in Maggie. Trust and safety: How we check facts.
Leo is an AI companion, not a veterinarian. For medical concerns, always consult your vet.
