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Dog age calculator — dog years to human years

A dog's age in human years depends on its size — a 7-year-old small dog and a 7-year-old giant breed are at very different life stages. This calculator adjusts for that.

Human age equivalent

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About this calculator

How dog aging works

All dogs age quickly in their first two years — equivalent to roughly 24 human years. After that, the rate depends on size:

SizeYearly human-year gain (after year 2)
Small (under 20 lb)~4 years/year
Medium (21–50 lb)~5 years/year
Large (51–100 lb)~6 years/year
Giant (over 100 lb)~7 years/year

Source: AKC dog age chart, adjusted for size.

Example

A 5-year-old medium dog: 24 human years (at age 2) + 3 more years × 5 = 39 human years.

References

Frequently asked

How does size affect a dog's age in human years?
Large and giant dogs age faster after year two than small dogs. A 10-year-old small dog is roughly 56 in human years; a 10-year-old giant breed may already be equivalent to 79.
Is the 7-to-1 ratio accurate?
No. The 7x rule is a rough average and ignores the faster aging in the first two years and the difference by size. Age-adjusted charts are more accurate.
What do the first two years equal in human years?
Year one is roughly 15 human years; year two brings it to about 24 — for all sizes.
What is the scientific formula for dog age?
A 2019 study (Wang et al., Cell Systems) proposed a formula based on DNA methylation: human age = 16 × ln(dog age) + 31. This calculator uses the simpler AKC size chart which is easier to apply and widely referenced.
How do I share my result?
Click "Share with my numbers" to copy a URL that saves your dog's age and size.

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