How do you calculate a dog's age in human years?

A dog's first year is roughly equivalent to 15 human years, and the second year adds about 9 more. After that, dogs age a few human years for each calendar year, with the exact rate depending on adult size — small breeds age more slowly in later years than large and giant breeds.

Is one dog year really seven human years?

No. The 'multiply by seven' rule is a myth. Dogs age much faster than that in their first two years and then slow down, with the rate varying by breed size rather than staying constant.

Do cats age the same way as dogs?

Cats follow a similar early curve to dogs — about 15 human years in the first year and 9 more in the second — but then age at a steadier roughly 4 human years per calendar year afterward, regardless of breed.

Why do small dogs live longer than large dogs?

Small breeds grow more slowly and reach a stable adult stage that lasts many years, while large and giant breeds grow faster early on and tend to enter their senior years several years earlier.

PETYEARS.EXE — Age Calculator

How old is your pet, really?

Aging speed depends on species and, for dogs, adult size — a Great Dane and a Chihuahua don't run on the same clock. Set your pet's profile below.

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Species

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Breed (dog)

Age, in years

Golden Retriever → large build (51–90 lb)

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Exact weight in lbs (optional, dogs only — overrides breed size for a more precise result)

28 human years, roughly

Adult

Life Stage Timeline

BIRTH SENIOR YEARS

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Want species facts and sizing charts? Check the Field Guide icon up top.

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FIELDGUIDE.TXT — Species Facts

Dogs age differently by adult size

A dog's adult weight class changes its aging curve more than almost anything else. Toy and small breeds pack roughly 15 human years into their first year alone, then settle into a long, slow plateau. Giant breeds mature a little slower at the start but reach their senior years much sooner — often by age 6 or 7, versus 9 or 10 for a small breed.

Size class	Adult weight	Example breeds	~5 yrs old in human years
Toy / small	Under 20 lb	Chihuahua, Pomeranian, Dachshund	~36
Medium	21–50 lb	Beagle, Border Collie, Bulldog	~37.5
Large	51–90 lb	Labrador, German Shepherd, Boxer	~37
Giant	91 lb+	Great Dane, Mastiff, Saint Bernard	~43

Further reading: Dog years by breed, a size guide · Why small dogs live longer

Cats mostly age on one curve

Unlike dogs, a cat's breed doesn't change its aging speed much — a Maine Coon and a Domestic Shorthair age at roughly the same rate. What matters far more is indoor vs. outdoor living: indoor cats commonly reach 13–17 years, while outdoor cats average closer to 2–5 due to traffic, disease, and predators.

Life stage	Cat age	~Human years
Kitten	0–1 yr	0–15
Young adult	1–2 yrs	15–24
Adult	2–11 yrs	24–60
Senior	11–15 yrs	60–76
Geriatric	15+ yrs	76+

Lifespan varies hugely by type

Reptiles don't share one aging curve at all — a leopard gecko and a tortoise are worlds apart. Lizards and snakes typically live 10–30 years depending on species and care, while tortoises are the outliers: some giant tortoises can outlive their owners by decades, given the right habitat and diet.

Type	Example species	Typical lifespan
Lizard	Leopard gecko, bearded dragon, iguana	10–20 yrs
Snake	Corn snake, ball python	15–30 yrs
Aquatic turtle	Red-eared slider, box turtle	20–40 yrs
Tortoise	Sulcata, Russian tortoise	50–100+ yrs

Lifespan scales with body size

Small birds live fast, large parrots live long — the size gap in birds is even bigger than in dogs. A budgie might only be with you for 5–10 years, while a macaw or cockatoo can live 50 years or more, often outliving the person who adopted them.

Type	Example species	Typical lifespan
Small bird	Budgie, canary, finch, lovebird	5–10 yrs
Medium bird	Cockatiel, conure, Quaker parrot	15–25 yrs
Large parrot	African grey, macaw, cockatoo	40–80 yrs