Dog & Cat Age Calculator
Convert your dog or cat's age into human years using the AKC size-banded chart and the AAFP feline life stages, with life-stage guidance, lifespan context, and the full year-by-year table.
Adult size
A 3-year-old medium dog is about
28 human years
Typical lifespan
13 years
23% of an average life
One pet year right now
4.0 human years
Ageing speed at this point in life
DNA methylation estimate
49 human years
16 × ln(age) + 31 — Wang et al., 2020
The other direction
Full chart — medium dog
| Dog age | Human years | Gained that year | Life stage |
|---|---|---|---|
| 1 | 15 | +15 | Young adult |
| 2 | 24 | +9 | Young adult |
| 3 | 28 | +4 | Young adult |
| 4 | 32 | +4 | Young adult |
| 5 | 36 | +4 | Young adult |
| 6 | 42 | +6 | Mature adult |
| 7 | 47 | +5 | Mature adult |
| 8 | 51 | +4 | Mature adult |
| 9 | 56 | +5 | Senior |
| 10 | 60 | +4 | Senior |
| 11 | 65 | +5 | Senior |
| 12 | 69 | +4 | Senior |
| 13 | 74 | +5 | Geriatric |
| 14 | 78 | +4 | Geriatric |
| 15 | 83 | +5 | Geriatric |
| 16 | 87 | +4 | Geriatric |
The "multiply by seven" rule is wrong
The seven-to-one rule appears to date from a 1950s observation that people lived to about 70 and dogs to about 10. It is arithmetic, not biology, and it breaks immediately at both ends of a dog's life.
A one-year-old dog is not a seven-year-old child. It is sexually mature, fully grown or nearly so, and has a complete set of adult teeth — closer to a human of 15. By the second birthday that has advanced to roughly 24. After that the curve flattens out, adding four to five human years annually rather than seven.
Ageing is fast where development is happening and slow once it stops. Any conversion that uses a single multiplier for the whole of life has to be wrong at one end or the other, and the seven-year rule manages both.
Size changes everything — for dogs
Across mammal species, bigger generally means longer-lived: an elephant outlives a mouse many times over. Within the dog species the relationship inverts. A Great Dane is elderly at six; a Chihuahua of the same age is middle-aged. Each extra 2 kg of adult body mass costs a dog roughly one month of life expectancy.
The leading explanation is growth rate. Large breeds reach 60–70 times their birth weight in a year, and that pace of cell division brings higher IGF-1 levels, more oxidative stress, and earlier cancer incidence. Giant breeds also take longer to finish growing — up to two years — which is why the chart above treats them separately from the first year onward.
Cats have no equivalent split. Domestic cats vary far less in adult size than dogs do, so a single curve covers the species: 15 human years in the first year, 24 by the second, and four per year after that.
Small dog
~14 years
senior from 10
Medium dog
~13 years
senior from 9
Large dog
~11 years
senior from 8
Giant dog
~9 years
senior from 6
What the epigenetic clock adds
In 2020 a UCSD team led by Tina Wang compared DNA methylation patterns in Labrador retrievers and humans and found the same age-related marks accumulating in both — but on different timescales. Fitting one to the other produced a formula: human age = 16 × ln(dog age) + 31.
It is the first mapping derived from molecular biology rather than from lifespan averages, and it explains why puppies feel so much older than the seven-year rule suggests. A one-year-old dog lands at 31; a four-year-old at about 53. Because it is a logarithm, ageing slows continuously instead of stepping down at fixed birthdays.
Its limits matter too. The study used a single breed, the fit is unreliable below one year, and it does not account for size at all — so a Chihuahua and a Great Dane get the same number. The calculator shows it alongside the AKC chart rather than instead of it: one is grounded in molecular ageing, the other in how long dogs of that size actually live.
Life stages and what they change
- Puppy / kitten (0–1 year): vaccinations, socialisation, and growth-appropriate food. Large-breed puppies need controlled calcium to avoid joint disease.
- Young adult: peak physical condition. Annual check-ups, weight monitoring, and dental care that pays off a decade later.
- Mature adult: metabolism slows while food portions usually do not. This is where most pets become overweight, which shortens life more reliably than almost anything else.
- Senior: vets recommend twice-yearly exams with bloodwork. Kidney disease and hyperthyroidism in cats, and arthritis in dogs, are far more treatable when caught early.
- Geriatric: the goal shifts to comfort — pain management, traction on slippery floors, accessible litter and water, and shorter but more frequent walks.
The one intervention with the best evidence
A 14-year Purina study following Labrador littermates found that dogs kept at a lean body condition lived a median of 1.8 years longer than their moderately-fed siblings — about 15% more life, and with later onset of arthritis. Keeping ribs easily felt but not visible is the single most effective thing an owner controls.
Estimating age without a birth certificate
For a rescue or stray, teeth are the most reliable guide. Puppies and kittens have all their baby teeth by 6–8 weeks and a full adult set by around 7 months. After that, tartar build-up and wear take over: light tartar on the back teeth suggests 1–3 years, noticeable staining and wear 3–5, and significant wear with possible tooth loss points to 5–10.
Other markers include the lens of the eye, which develops a bluish haze (lenticular sclerosis) from about seven years in dogs, muscle tone over the spine and hind legs, and coat quality — greying around the muzzle starts earlier in large breeds and is a weak signal on its own.
These conversions are population averages. Breed, genetics, diet, dental care, and whether a pet is neutered all shift the real figure. Nothing here replaces an examination by a vet, who can date an animal far more accurately than any chart.