Human years to dog years calculator
Enter a human age to see the dog age that matches it. Dogs age faster when young and at different speeds by size, so the answer depends on the size of the dog. A chart follows below.
For a medium dog
- Research formula (2020)
- —
- Old 7 to 1 rule
- 2.6
Human years to dog years chart
| Human age | Small dog | Medium dog | Large dog | Giant dog | Research formula | 7 to 1 rule |
|---|---|---|---|---|---|---|
| 10 | 0.7 | 0.7 | 0.7 | 0.7 | — | 1.4 |
| 15 | 1.0 | 1.0 | 1.0 | 1.0 | — | 2.1 |
| 18 | 1.3 | 1.3 | 1.3 | 1.3 | — | 2.6 |
| 20 | 1.6 | 1.6 | 1.6 | 1.6 | — | 2.9 |
| 21 | 1.7 | 1.7 | 1.7 | 1.7 | — | 3.0 |
| 25 | 2.2 | 2.2 | 2.2 | 2.2 | — | 3.6 |
| 30 | 3.5 | 3.4 | 3.1 | 3.0 | — | 4.3 |
| 40 | 6.0 | 5.7 | 5.0 | 4.7 | 1.8 | 5.7 |
| 50 | 8.5 | 7.8 | 6.9 | 6.1 | 3.3 | 7.1 |
| 60 | 11 | 10 | 8.8 | 7.5 | 6.1 | 8.6 |
| 70 | 13 | 12 | 11 | 8.9 | 11 | 10 |
| 80 | 16 | 14 | 13 | 10 | 21 | 11 |
Values are dog ages in years. Ages beyond about 15 dog years are extended from the chart and are less certain, since few dogs live that long.
How it works
This is the reverse of the dog years to human years calculator. That calculator turns a dog's age into human years using a size chart. Here we find the dog age whose human equivalent matches the age you enter. A dog reaches about 15 human years in its first year and 24 in its second, which is why a teenager matches a dog of only a year or two.
Solved for the dog's age, that is dog age = e(human age − 31) / 16. The old rule of one dog year for every seven human years is popular but crude, and it is shown only for comparison. The research formula was built from Labrador Retrievers, so it is a rough comparison for other breeds.
Questions
How old am I in dog years?
It depends on the size of the dog you compare with. At 30 human years you match a medium dog of about 3.4 years, while the old rule gives about 4.3.
Is a dog year really seven human years?
No. Dogs age very quickly in their first two years and then more slowly, and bigger dogs age faster later in life. The size chart and the research formula are both closer to reality than multiplying by seven.
How old is an 18 year old in dog years?
About 1.3 years for a medium dog by the size chart. A dog reaches the human equivalent of 18 early in its second year.
Why does the research formula show a dash for young ages?
It only applies from a dog age of one year, which is a human age of 31.
I want to convert my dog's age.
Use the dog years to human years calculator. For cats see cat years to human years.
Sources
- American Animal Hospital Association (AAHA), canine and feline age chart, human-year equivalents by dog size.
- Wang T. et al., "Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome", Cell Systems, 2020 (University of California San Diego).
Last reviewed 2026-10-26.