Dog Age Calculator
Forget "multiply by 7." Enter your dog's age and size class to get a research-backed human-equivalent age — plus their life stage.
Your dog
Size adjusts the formula: small dogs age slightly slower, giant dogs faster.
Why "multiply by 7" is wrong
Dogs mature extremely fast in their first two years — a 1-year-old dog is roughly equivalent to a 31-year-old human, not a 7-year-old. After that, aging slows down. In 2019, researchers at UC San Diego (Wang et al., Cell Systems) quantified this by comparing DNA-methylation "epigenetic clocks" in Labrador Retrievers and humans, producing the formula:
The study used Labradors, so we adjust for size class: small ×0.92, medium ×1.0, large ×1.06, giant ×1.12. This is still an approximation — breed, weight, and health history all shift the curve — but it's far closer to biology than the old rule of thumb.
What the life stage means
Under 2 years. Rapid growth, training-heavy, highest first-year costs (vaccines, spay/neuter, setup). This is also when the cost calculator's 1.35× first-year multiplier bites.
The steady years. Routine vet care, stable food costs, and the best window to build the emergency fund you'll want later.
Giant breeds from ~6, large ~7–8, medium ~9, small ~10. Expect twice-yearly vet visits, senior bloodwork, and rising healthcare spending — see our senior care guides.
Frequently asked questions
Is the "multiply by 7" rule for dog years accurate?
No. A 2019 UCSD study found the relationship is logarithmic: a 1-year-old dog is about 31 in human years, a 5-year-old large dog about 60, and a 10-year-old about 68. The old rule underestimates young dogs and overestimates old ones.
Does dog size affect aging?
Yes. Small dogs generally live longer and age more slowly than large dogs, which is why giant breeds become seniors around age 6 while small breeds may not until 10. Our calculator applies size adjustments to the base formula.
At what age is a dog considered a senior?
It depends on size: giant breeds around 6, large breeds around 7–8, medium breeds around 9, small breeds around 10. Read our full guide: when is my dog considered a senior?
Now price out the years ahead
Senior years cost more — mostly at the vet. Run your breed through the cost calculator to see the full lifetime picture.