Dog Age Calculator
Convert your dog's age into human years using the modern, size-based method vets recommend — not the old 'multiply by 7' myth. Small, medium, large and giant breeds all age differently.
Dog age calculator
Dog years → human years, by breed size.
A friendly estimate. Your vet can give the best guide to your dog's life stage and health.
How old is my dog in human years?
For decades people multiplied a dog's age by seven to get its "human age". It's a memorable rule — and almost entirely wrong. Dogs mature very quickly in their first two years and then age more slowly, and crucially, smaller breeds live longer than giant ones. This calculator uses a size-aware approach much closer to how vets actually think about canine ageing.
A one-year-old dog is roughly a 15-year-old human; by age two it's around 24. After that, each dog year adds about 4–6 human years depending on size — fewer for small breeds, more for giant ones.
Why size changes everything
It seems counter-intuitive, but large and giant breeds age faster and have shorter lifespans. A Great Dane may be considered "senior" by six or seven, while a small terrier can stay sprightly well into its teens. That's why a single multiplier can't be accurate — a seven-year-old Chihuahua and a seven-year-old mastiff are at very different life stages.
Dog age conversion chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 14 |
| 2 years | 23 | 24 | 24 | 22 |
| 5 years | 36 | 37 | 40 | 45 |
| 10 years | 56 | 60 | 66 | 80 |
| 13 years | 68 | 74 | 82 | 101 |
Life stages, not just numbers
Vets increasingly talk about life stages — puppy, young adult, mature adult, senior — rather than a precise human-age figure, because health and breed matter as much as the calendar. Knowing roughly where your dog sits helps with the right diet, exercise and check-up schedule. Senior dogs, for example, benefit from more frequent vet visits and adjusted nutrition.
A fun fact. A 2019 study suggested a logarithmic formula based on DNA methylation, which is why the first dog year counts for so much more than later ones. Our size-based method captures the same "fast then slow" curve in an easy way.
Frequently asked questions
How do you calculate a dog's age in human years?
Modern methods count the first year as about 15 human years, the second as roughly 9 more (reaching ~24), then add 4–6 human years per dog year depending on breed size. The old 'multiply by 7' rule is inaccurate.
Is one dog year really seven human years?
No. That rule of thumb is a myth. Dogs mature rapidly early on, then age more slowly, and small breeds age slower than large ones — so a flat multiplier doesn't work.
Do small dogs live longer than big dogs?
Generally yes. Small breeds often live 14–16 years or more, while giant breeds may only reach 7–10. That's why size is built into this calculator.
At what age is a dog considered a senior?
It varies by size: giant breeds can be senior by 6–7, large breeds around 8, and small breeds not until 10–12. Your vet can confirm your dog's life stage.
Is this dog age calculator accurate?
It's a close, friendly estimate based on the veterinary consensus that ageing is fast then slow and size-dependent. For health decisions, always consult your vet.