Dog Age Calculator: How Old in Human Years? Compare by Size
A three-year-old dog is not always comparable to a 21-year-old person. Early development and adult size change the comparison. This calculator uses an AAHA comparison chart rather than multiplying every age by seven.
How old is your pet in human years?
Choose your pet and actual age. The initial values are an example.
Inputs stay in this browser; the calculator does not send or save them.
Why does dog size matter?
The source chart separates dogs into four adult weight bands. For example, a ten-year-old small dog corresponds to about 56 human years; the giant-dog comparison is about 78. These are reference comparisons, not biological ages measured for your dog.
| Actual age | Small dog | Medium dog | Large dog | Giant dog | Cat |
|---|---|---|---|---|---|
| 1 years | 15 | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 | 24 |
| 3 years | 28 | 28 | 30 | 32 | 28 |
| 5 years | 36 | 37 | 40 | 42 | 36 |
| 7 years | 44 | 47 | 50 | 56 | 44 |
| 10 years | 56 | 60 | 66 | 78 | 56 |
| 15 years | 76 | 83 | 93 | 115 | 76 |
How are months calculated?
Whole ages use the chart values. Between listed ages, PetNyam interpolates proportionally and rounds to one decimal. For example, a small dog aged 3 years 6 months falls halfway between 28 and 32, giving about 30 human years.
Dog comparisons cover 1–20 years, except giant dogs, for which the chart ends at 16 years. Cat comparisons cover 6 months–21 years. We display no numerical estimate outside those ranges.
What about rabbits, hamsters and parrots?
This calculator does not apply dog or cat age curves to other species. Parrot species also vary widely, so a single generic parrot ratio would be misleading. Keep the actual age and species in your care records and consult a veterinarian familiar with that animal.
What should I do with the result?
Use it as a prompt to review care records, not to choose food portions, medicines or testing on your own. Record changes in appetite, activity and weight for your veterinarian; the comparison cannot diagnose illness or predict lifespan.
Can dogs eat apples? · Can cats drink milk? · New food checklist (Korean)
Sources and calculation limits
AAHA/Zoetis physiological age comparison chart (PDF) supplies the dog-size and cat reference values. UC Davis veterinary explanation discusses the limits of simple ratios and breed-specific research. Monthly interpolation is PetNyam’s display method, not a method validated by AAHA.
Published and sources checked: October 28, 2026. PetNyam age comparisons are informational estimates, not veterinary assessments.