Houndyear · Reverse calculator
How many dog years is that?
Convert human age to dog age.
Enter your age and pick a dog size to see your dog-year equivalent.
Enter your age and pick a dog size to see your dog-year equivalent.
Based on AAHA Canine Life Stage Guidelines and the UC San Diego DNA methylation study. An estimate — not a clinical diagnosis.
The Science
The old “seven dog years per human year” rule isn't how dogs age.
Dogs mature very fast in their first two years — a one-year-old dog is roughly fifteen in human years, and a two-year-old is around twenty-four. After that, the pace depends almost entirely on body size.
Our calculator combines the AAHA Canine Life Stage Guidelines (2019) with the UC San Diego DNA methylation study (Wang et al., 2020) — the same research framework veterinarians use when discussing aging with pet parents. Small dogs age about 4 human years per dog year after age 2; medium 5; large 6; giant breeds 7.
It's an estimate for everyday use — not a clinical tool. Your vet remains the best source for health-specific guidance.
The other way around
Want your dog's age in human years instead?
Use the main dog age calculator — enter their age and size to find their human-equivalent age.
Try the dog age calculator →
Common questions
About the reverse calculation.
How accurate is the reverse calculation?
It's a science-based estimate, not a clinical conversion. The formula uses the same AAHA Canine Life Stage Guidelines (2019) and UC San Diego DNA methylation research (Wang et al., 2020) that power the forward calculator — applied in reverse to map a human age back to its dog-equivalent.
What's the underlying formula?
For the first 15 human years, divide by 15 (a 1-year-old dog ≈ a 15-year-old human). From 15 to 24 human years, dogs add about 9 human years per dog year. After 24 human years, dogs age at 4 (small), 5 (medium), 6 (large), or 7 (giant) human years per dog year. The reverse simply inverts that mapping.
Why does dog size affect the math?
Body size is the single strongest predictor of canine lifespan. Larger dogs accumulate cellular damage faster, age more quickly, and live shorter lives — that's why a 5-year-old Chihuahua and a 5-year-old Great Dane are at very different biological points despite the same calendar age.
Is this medical advice?
No — Houndyear is for educational purposes only. The reverse calculator is a thought experiment based on averaged research data, not any individual dog's clinical biological age. Always consult your veterinarian for health decisions.