Dog Age Calculator
The old "multiply by 7" rule is wrong: dogs mature fast early, then age slower. This calculator uses the size-adjusted veterinary method and shows the 2019 epigenetic (DNA-based) formula alongside.
Results
How dog age conversion really works
Dogs don't age at a constant rate. A one-year-old dog is roughly a 15-year-old human; by age two they're about 24 in human years. After that, aging slows to a size-dependent rate — and counterintuitively, bigger dogs age faster:
| Size | Weight | Rate | 10-year-old dog is… |
|---|---|---|---|
| Small | < 20 lb | +4 / year | 56 human years |
| Medium | 20–50 lb | +5 / year | 64 human years |
| Large | 50–90 lb | +6 / year | 72 human years |
| Giant | > 90 lb | +7 / year | 80 human years |
In 2019, researchers at UC San Diego compared DNA methylation ("epigenetic clocks") in Labradors and humans and derived a formula: human age = 16 × ln(dog age) + 31. It confirms the fast-early pattern — a 1-year-old dog maps to a 31-year-old human epigenetically — though it flattens out more in later years than vets observe behaviorally.
Why the ×7 rule survives anyway
The "multiply by 7" rule dates to the 1950s, when humans lived to ~70 and dogs to ~10. It was marketing math, not biology — but it stuck because it's easy. It badly underestimates how mature young dogs are (a 1-year-old dog can reproduce; a 7-year-old human can't) and overestimates aging in small senior dogs.
Frequently asked questions
How old is my dog in human years?
Count 15 human years for the first dog year, 9 for the second, then 4–7 per year depending on size: small dogs +4, medium +5, large +6, giant +7 per year.
Is the 7 dog years rule true?
No. It's a 1950s simplification. Dogs reach the equivalent of their mid-20s in human terms by age two, then age more slowly — at a rate that depends on their size.
Why do large dogs age faster than small dogs?
It's one of biology's odd exceptions — across species, bigger animals live longer, but within dogs, every extra 4.4 lb of body mass cuts life expectancy by about a month. The leading theory involves faster growth driving earlier cell damage.
What is the epigenetic dog age formula?
human age = 16 × ln(dog age) + 31, from a 2019 UC San Diego study matching DNA methylation patterns between Labradors and humans. It's most meaningful for dogs over one year old.