🐶 Dog Age Calculator
Dogs age faster than humans, but the old multiply-by-7 rule is a myth. Real canine aging is front-loaded — the first year equals about 15 human years — and larger breeds age faster in their later years than small ones.
This calculator converts your dog's age to human-equivalent years, adjusting for breed size, and shows the current life stage from puppy to senior.
How to use this calculator
Enter your dog's age, pick small, medium or large for breed size, and read the human-equivalent age.
- Type your dog's age in years.
- Select the breed size closest to your dog.
- Read the human-equivalent age and life-stage label.
How Old Is My Dog in Human Years by Breed Size?
Size matters for dogs: a 5-year-old small dog is about 36 in human years, while a 5-year-old large dog is closer to 42, because big breeds age faster once adult. The formula counts the first year as 15 human years and the second as 9, then adds 4 per year for small breeds, 5 for medium and 6 for large. Giant breeds like Great Danes are seniors by 6 or 7, while a Chihuahua may still be sprightly at 14.
Frequently asked questions
Is the 7 dog years rule true?
No. It is a rough myth — real aging is faster early on. One dog year is about 15 human years, the second about 9, and only later years settle near 4-6 each depending on size.
Why do big dogs age faster than small dogs?
Large breeds grow faster and their cells divide more rapidly, which seems to accelerate aging. A Great Dane's life expectancy is 7-10 years while a Chihuahua often reaches 15-18.
When is a dog considered a senior?
Roughly 7 for large breeds and 9-10 for small breeds. Senior dogs benefit from joint supplements, softer food and more frequent vet checks.
How old is a 10 year old dog in human years?
About 56 for a small dog, 64 for a medium dog and 72 for a large dog — the size gap widens with age.
Do mixed breeds follow the same formula?
Yes, use the size setting closest to your dog's adult weight. Mixed breeds often enjoy hybrid vigor and may outlive purebreds of similar size.