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Dog & Cat Age Calculator
Your pet
A pet that is 5 years and 6 months old counts as 5.5 years.
A rough estimate based on the widely used AVMA-style rule: 15 human years for the first year, 9 for the second, then 5 a year for dogs and 4 a year for cats. It is not veterinary advice — size, breed and health all affect how a pet ages.
Example: a 5-year-old dog is 39 in human years (15 + 9 + 3 × 5), and a 5-year-old cat is 36 (15 + 9 + 3 × 4).
Behind the numbers
How pet age converts to human years
Dogs and cats mature fast in their first two years and then age more slowly, so a straight “multiply by 7” is wrong. The widely used AVMA-style rule counts the first year as 15 human years, the second year as 9 more, and every year after that as 5 human years for a dog and 4 for a cat. A pet under 1 year old is scaled proportionally through that first year.
Worked example: a 5-year-old dog. The first year counts as 15 human years, the second as 9, and each of the 3 years after that as 5 — so 15 + 9 + 3 × 5 = 39 human years. A 5-year-old cat: 15 + 9 + 3 × 4 = 36 human years. A 6-month-old dog is about 7.5 human years (half of the first year’s 15).
A few comparisons
Example ages in human years
| Pet age | Dog | Cat |
|---|---|---|
| 6 months | 7.5 human years | 7.5 human years |
| 1 year | 15 human years | 15 human years |
| 2 years | 24 human years | 24 human years |
| 3 years | 29 human years | 28 human years |
| 5 years | 39 human years | 36 human years |
| 7 years | 49 human years | 44 human years |
| 10 years | 64 human years | 56 human years |
| 15 years | 89 human years | 76 human years |
Age is a guide, not a verdict.
Size matters for dogs: small breeds tend to live longer and age more slowly than giant breeds, so a 7-year-old Great Dane is older, in body terms, than a 7-year-old Chihuahua.
Senior pets need checkups twice a year, not once — bloodwork and dental checks catch the problems that age brings before they become emergencies.
Keep a senior pet lean and moving: extra weight and no exercise age joints faster than the calendar does.
A sudden change — drinking much more water, losing weight, or sleeping all day — matters more than the number on this page, so mention it to your vet.
Good to know
Your pet age questions, answered.
Why not just multiply my pet’s age by 7?
The “multiply by 7” rule is a myth. Dogs and cats mature very fast in their first two years — a 1-year-old dog is roughly a 15-year-old human, not a 7-year-old — and then age more slowly. The 15 + 9 + 5 (dogs) or + 4 (cats) rule follows their real growth curve much better.
Does breed or size change the answer?
Yes, especially for dogs. Small breeds age more slowly and live longer than large and giant breeds, so a 10-year-old small dog is “younger” than a 10-year-old large dog. This calculator uses the general rule for all dogs and cats, so treat the result as a rough guide.
Is this veterinary advice?
No. This is a rough estimate for fun and general guidance. Your vet can judge your pet’s real condition from weight, teeth, bloodwork and behaviour, which no age formula can see.
When is a pet a senior?
As a rough guide, dogs are seniors from about 7 years old (earlier for large breeds), and cats from about 11 years old. A senior pet benefits from twice-yearly vet visits and a diet and exercise plan for older animals.