Pet Age to Human Age Calculator

Pet Size adjusts the per-year aging rate that kicks in after age two, and that size-linked pattern -- larger dog breeds maturing and aging faster than small ones -- is specific to dogs. This calculator applies a single per-year rate to cats regardless of size for ages beyond two, since size has a much smaller documented effect on feline aging than it does on canine aging.

No -- the first year alone accounts for 15 human years, the second year adds 9 more (reaching 24), and every year after that adds a much smaller amount (roughly 4 to 6 years depending on species and dog size). Raising Pet Age always raises Human Age Equivalent, but the size of each additional year's contribution shrinks sharply after age two.

Only past age two -- before that, all dogs (and cats) follow the same first-two-year curve regardless of size. Past age two, a large dog's human-year equivalent grows faster than a same-age small dog's, since large breeds are assigned a bigger per-year increment (about 6 years versus about 4 for small breeds).

Age Difference is simply Human Age Equivalent minus the pet's actual age in years, showing how much of a gap has opened up between the two. Because the human-year rate is always at least as fast as the pet's own aging rate at every stage of this formula, that gap widens every additional year rather than narrowing.