Is the 7-year rule true?
No. Multiplying a pet’s age by seven is easy to remember, but it is wrong at almost every age, and it ignores the biggest factor for dogs: size.
The ×7 rule against the vet chart
| Age | ×7 rule | Small dog | Giant dog | Cat |
|---|---|---|---|---|
| 1 | 7 | 15 | 12 | 15 |
| 2 | 14 | 24 | 22 | 24 |
| 5 | 35 | 36 | 45 | 36 |
| 10 | 70 | 56 | 79 | 56 |
| 15 | 105 | 76 | 114 | 76 |
Where the rule goes wrong
Puppies and kittens grow up fast. Most reach maturity within their first year, which is why vets put a one-year-old at roughly 12 to 15 human years, not 7. By two they are in their mid-twenties.
After that, aging slows down, and for dogs the pace depends on size. A small dog adds about four human years per year and can live to 15 or more. A giant breed adds about seven or eight and is a senior at six or seven. One multiplier cannot describe both.
Where did ×7 come from?
Nobody knows for sure. The most commonly cited explanation is that it started as a rough ratio between average human and dog lifespans (about 70 and 10 years) and stuck because it was simple. It was never based on how dogs actually mature.
What to use instead
The size-based vet chart, which our dog age calculator and cat age calculator use by default. For the full comparison, including the DNA-based formula, see how pet age is calculated.
FAQ
Is a dog year 7 human years?
No. A one-year-old dog is about 12 to 15 in human years depending on size, and after age two each year adds 4 to 9 human years depending on size.
Is a cat year 7 human years?
No. Cats are about 15 at one and 24 at two, then age about four human years per year.