How Old is a 3-Year-Old Dog in Human Years?
A 3-year-old medium dog is roughly equivalent to a 28-year-old human.
How to use this tool
- Enter your dog's age in years.
- Select their breed size category.
- Read the equivalent human-year age below.
A 3-year-old dog is fully mature and energetic, corresponding roughly to a person in their late twenties.
Frequently asked questions
- Why do large dogs age faster?
- Larger breeds have shorter average lifespans (8–12 years vs 14–16 for small breeds), meaning each calendar year represents more biological ageing. The exact mechanism isn't fully understood but may relate to faster growth rates.
- Is the 7× rule accurate?
- No. The old '1 dog year = 7 human years' rule ignores breed size and non-linear ageing — dogs mature very quickly in their first two years and then slow down.