Pet Age Calculator
A research-grade conversion of your dog or cat\u2019s age into human-equivalent years. No "multiply by seven" — that rule has been wrong for decades.
Why "1 dog year = 7 human years" is wrong
The seven-to-one rule is a marketing slogan from the 1950s designed to encourage annual veterinary check-ups. The actual relationship is much steeper at the start of life and much shallower after maturity. A one-year-old dog is closer to a 15-year-old human in terms of physical and reproductive development, not a seven-year-old.
The modern dog formula
The 2020 UCSD epigenetic-clock study introduced a logarithmic conversion based on DNA methylation patterns: human_years ≈ 16 × ln(dog_years) + 31. This works very well for medium-sized dogs older than two years. We extend it with the long-standing veterinary observation that small breeds live longer than giant breeds, applying a size-aware adjustment.
The modern cat formula
Cats develop rapidly: by the end of year one they have reached the human equivalent of about 15 years; by the end of year two, about 24. From then on, each additional calendar year adds roughly four human years. This staircase is the consensus model used by feline veterinary associations.
Life stages we report
- Puppy / Kitten — under 1 year
- Junior / Young adult — 1–2 years
- Adult — 3–6 years
- Mature — 7–10 years
- Senior — 11+ years (sooner for giant breeds)
Frequently asked questions
Is one dog year really seven human years?
No. The "1:7" rule is a comforting myth from the 1950s. Modern veterinary research, including the 2020 epigenetic-clock study from UC San Diego, shows the relationship is logarithmic — dogs age very fast in their first two years and then slow down considerably.
Why does dog size matter?
Larger breeds have shorter lifespans and age faster after maturity. A Great Dane at age seven is biologically older than a Chihuahua at age seven, even if their veterinary chart age is identical.
How is the cat formula different?
Cats reach the equivalent of 15 human years by their first birthday and 24 human years by their second. After that, each additional cat year adds about four human years.