Dog age in human years
Put your dog's age in and get the human equivalent, based on how dogs actually mature rather than the multiply-by-seven rule.
The old rule of multiplying by seven does not match how dogs actually age. They mature very quickly in the first two years and more slowly afterwards, which is what this works from. Size matters too: larger breeds age faster than small ones, so treat this as a rough guide.
Why multiplying by seven never worked
The seven-year rule appears to have come from a rough comparison of average lifespans decades ago, and it survives because it is easy to remember. The problem is that it assumes dogs age at a constant rate, and they do not. A one-year-old dog is not a seven-year-old child: they are physically mature, capable of reproducing, and finished growing. That is much closer to a human teenager.
This calculator uses the more widely cited version instead: the first year is worth about 15 human years, the second adds roughly nine more, and each year after that adds about five.
Size changes the answer
The biggest thing no simple formula captures is body size. Small breeds tend to live considerably longer than giant ones, and the gap is large enough to matter. A Great Dane may be considered geriatric at six or seven, while a Jack Russell of the same age is barely middle-aged.
So if you own a large or giant breed, assume your dog is a little older than this calculator suggests, and if you own a small one, a little younger. It is a rough guide either way.
What ageing actually looks like
The number matters less than what you notice. Slowing down on walks, stiffness after rest, cloudier eyes, less interest in play, disturbed sleep, or changes in toileting are all worth mentioning to your vet rather than filing under getting old. Plenty of them are treatable, and pain in particular is very often mistaken for age.
Most vets recommend moving to twice-yearly check-ups once a dog reaches their senior years, which for a large breed can be as early as six.