How this calculator works
Dogs mature much faster than humans in their first two years, then aging slows down — and the rate depends heavily on adult size. Larger breeds age faster in their senior years than small breeds. This tool uses commonly cited veterinary size-based aging curves instead of the oversimplified "1 dog year = 7 human years" rule.
General guide by size
- Small breeds (Chihuahua, Yorkie): age slower after year two, often living 14–16 years.
- Medium breeds (Beagle, Cocker Spaniel): moderate aging pace, typically 12–14 years lifespan.
- Large breeds (Labrador, German Shepherd): age faster after year five, typically 10–13 years lifespan.
- Giant breeds (Great Dane, Mastiff): age fastest, typically 7–10 years lifespan.
This tool is for general information only and isn't a substitute for veterinary advice about your specific dog's health.
We publish the exact dog age formula, including the size-based rates and its limitations.
See the methodology →Sources
Quick reference: dog age by size
| Dog's age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 5 years | 36 | 38 | 39 | 42 |
| 10 years | 56 | 60 | 64 | 72 |
| 15 years | 76 | 83 | 89 | 102 |
See the full breakdown in the Dog Age Chart.
Frequently asked questions
How accurate is this dog age calculator?
It's a general estimate based on commonly cited veterinary size-based aging curves, which are more accurate than the flat "multiply by 7" rule. Individual dogs still vary based on genetics, health, and breed-specific factors, so treat the result as a ballpark rather than exact.
Is 1 dog year really equal to 7 human years?
No, that's an oversimplified myth. A 1-year-old dog is closer to 15 in human years, and a 2-year-old dog is closer to 24, since dogs mature much faster than humans in their first two years. Aging speed after that depends heavily on adult size.
What age is a dog considered a senior?
It varies by size: small breeds are often considered senior around 10-12 years old, medium breeds around 8-10, large breeds around 7-8, and giant breeds as early as 6, since larger dogs age faster in their later years.
Do all dog breeds age at the same rate?
No. The first two years look similar across sizes, but after that, larger breeds age faster than smaller ones. A giant breed can add roughly 6 human years per dog year in adulthood, compared to about 4 for a small breed. See Puppy Age in Human Years for the early stretch specifically.
How old is a 2-year-old dog in human years?
About 24 in human years, which is fairly consistent across nearly all adult sizes at this age. The size-based differences become more significant after age two — see How Old Is My Dog in Human Years? for the full explanation.