What does this tool do?
The old seven-years-per-year rule ignores how quickly pets mature early in life. This calculator uses the common veterinary rule of thumb: 15 human years for the first year, 9 for the second, then a size-dependent rate.
The Formula
Human years = 15 × age (year one), 24 at year two, then 24 + (age − 2) × 4–6Frequently Asked Questions
Why is the seven-year rule inaccurate?
Pets mature much faster than humans in their first two years, then age more slowly. A dog is roughly 15 human years old at one and about 24 at two, so a flat seven-year rate overstates young ages.
Do mixed-breed pets age differently?
Size is a stronger predictor than breed for dogs: small dogs generally live longer than large ones. Cats age on a similar curve regardless of breed.