Dog Years to Human Years Calculator

This calculator converts a dog’s age into “human years” with a widely used rule of thumb: the first year counts as 15, the second as 9, and each year after that as about 5. Enter the dog’s age in years (decimals for months are fine); you get the equivalent human age.

Formula

This is the rule of thumb popularised by the American Veterinary Medical Association (AVMA) for medium-sized dogs. Human years = 15 × (first year) + 9 × (second year) + 5 × (each year after two). In symbols: 15·min(a, 1) + 9·min(max(a − 1, 0), 1) + 5·max(a − 2, 0).

• a: the dog’s age in years; 6 months is 0.5

Worked Example

A 5 year old dog.

1. First year: 15
2. Second year: + 9 = 24
3. Three more years: + 3 × 5 = 15
4. Human age = 39.0 years

How to read the result

The rule reflects that dogs grow up fast in the first two years and age more slowly after. Small breeds tend to age more slowly in later years and giant breeds faster, so read the result as a rough comparison, not a health measure. Your vet is the person to ask about your dog’s health at any age.

Limits and common mistakes

• The “multiply by 7” rule overstates puppies’ age and understates young adults’.
• No single formula fits all breeds and sizes.
• This is a comparison for fun and conversation, not veterinary advice.

Frequently Asked Questions

How old is a 1 year old dog in human years?

About 15.

Is one dog year seven human years?

Not really; the first two years count for much more.

How old is a 10 year old dog?

About 64 by this rule.

Does breed size matter?

Yes. Large breeds generally age faster in later life, small breeds slower.

in a | Dog's age | years | 5 | 0 | 30
out h | Equivalent human age | years | 15 * min(a, 1) + 9 * min(max(a - 1, 0), 1) + 5 * max(a - 2, 0) | 1