Veterinarian Approved Method
Dog Age Calculator
Calculate your dog's true age in human years using the latest veterinary science that accounts for size and growth rates.
1 years
ℹ️ Small: <20 lbs • Medium: 20-50 lbs • Large: 50-90 lbs • Giant: 90+ lbs
Human Equivalent15years old
📏 Why Size Matters
Unlike most mammals, small dog breeds typically live significantly longer than large breeds. A Great Dane might be considered "senior" at age 6, while a Chihuahua is still in their prime.
Our calculator adjusts for this biological difference. Giant breeds age rapidly after their second year (approx. 7 human years per dog year), while small breeds age more slowly (approx. 4 human years per dog year).
🧪 The Science
- 1First Year: All dogs develop rapidly, reaching the equivalent of 15 human years.
- 2Second Year: Development slows slightly, adding about 9 human years.
- 3Adulthood: Aging rate diverges based on weight and breed size.
Frequently Asked Questions
How do you calculate dog years to human years?▼
The old "multiply by 7" rule is outdated. The first year of a dog's life equals about 15 human years. The second year is about 9 human years. After that, each dog year equals 4-5 human years for small/medium dogs and 6-7 years for large/giant breeds.
Why do small dogs live longer than large dogs?▼
Scientists believe large dogs age faster biologically because they grow so rapidly from puppyhood to adulthood. This accelerated growth places stress on their bodies (oxidative stress), leading to earlier age-related diseases. Small breeds like Chihuahuas can live 15-20 years, while Great Danes often live only 7-10 years.
When is a dog considered a senior?▼
It depends on size. Small dogs are considered seniors around 10-12 years. Medium dogs around 8-9 years. Large and giant breeds are considered seniors as early as 6-7 years old.
What is the oldest dog on record?▼
The Guinness World Record for the oldest dog ever is held by Bobi, a Rafeiro do Alentejo from Portugal, who lived to be 31 years and 165 days old. Previously, an Australian Cattle Dog named Bluey lived to 29 years.
Lifespan by Breed
Curious about a specific breed? Check their average lifespan.