Calculate your dog’s age in human years from your dog’s age in dog years.
Dog Age Formula
This calculator can convert age in four different ways, and it can also work backward from a human-year equivalent to a dog's actual age. The mode you pick controls which formula is used.
Epigenetic: HumanAge = 16 * ln(DogAge) + 31
Seven-year rule: HumanAge = 7 * DogAge
AVMA: HumanAge = 15 (first year) + 9 (second year) + 5 * (DogAge - 2)
- HumanAge = the dog's age expressed in human years
- DogAge = the dog's actual age in years (months are added as a fraction)
- ln = the natural logarithm
- Size = the dog's adult weight band (small, medium, large, or giant), used by the size-adjusted method
The epigenetic method comes from a study of DNA methylation patterns and gives a curved conversion that ages dogs quickly when young and slowly when older. The seven-year rule is the old shortcut that simply multiplies by seven. The AVMA method counts the first year as 15 human years, the second year as 9 more, and every year after that as 5 more. The size-adjusted method uses the same fast-then-slow pattern but shifts the result by your dog's adult size, since small dogs tend to live longer and age more slowly than giant breeds. The compare mode runs all methods at once so you can see the spread, and the reverse mode estimates a dog's real age from a human-year figure.
Human-Year Equivalents by Size
The table below shows roughly how many human years a dog has reached at common ages, broken out by adult size. Use it as a quick check against the calculator.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 14 |
| 2 years | 24 | 24 | 22 | 22 |
| 5 years | 36 | 37 | 40 | 45 |
| 8 years | 48 | 51 | 55 | 64 |
| 12 years | 64 | 69 | 77 | 93 |
Size bands follow the common adult-weight groupings: small is 20 lb or less, medium is 21 to 50 lb, large is 51 to 100 lb, and giant is over 100 lb.
Examples
Example 1. A 4-year-old dog using the epigenetic formula: HumanAge = 16 * ln(4) + 31 = 16 * 1.386 + 31 = 22.2 + 31 = about 53 human years.
Example 2. A 3-year-old dog using the AVMA method: 15 + 9 + 5 * (3 - 2) = 15 + 9 + 5 = 29 human years.
FAQ
Why do the methods give different answers? Each method models aging differently. The seven-year rule is a flat multiplier, the AVMA method front-loads the first two years, and the epigenetic and size-adjusted methods use a logarithmic curve that better matches how dogs actually mature. The compare mode shows all of them side by side so you can judge the range.
Which method is most accurate? The epigenetic formula is based on measured DNA changes and tends to track real aging better than the seven-year rule, especially in the early years. That said, it came from a single breed, so the size-adjusted estimate can be closer for very small or very large dogs.
Does size really change how a dog ages? Yes. Small dogs usually mature quickly but live longer, so they age more slowly in later years. Giant breeds reach middle and old age faster, which is why their later-year equivalents in the table climb higher than those of small dogs.
