Dog years to human years chart
Dogs grow up fast: a one-year-old dog is about as mature as a 15-year-old person, and a two-year-old is about 24. After that, small dogs age more slowly than big ones, which is why the chart splits by size.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 28 | 30 | 32 |
| 4 | 32 | 33 | 35 | 37 |
| 5 | 36 | 37 | 40 | 42 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 78 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 101 |
| 14 | 72 | 78 | 88 | 108 |
| 15 | 76 | 83 | 93 | 115 |
| 16 | 80 | 87 | 99 | 123 |
Sizes: small up to 20 lb (9 kg), medium 21–50 lb, large 51–90 lb, giant over 90 lb (41 kg). Between whole years the calculator takes the in-between value, and puppies under one year are counted along the way to 15.
Is one dog year really seven human years?
No – the old “multiply by 7” rule is too low for young dogs and too high for old small dogs. A one-year-old dog is already a teenager, not a seven-year-old child.
The DNA-based formula
A 2019 study at the University of California, San Diego compared the ageing of DNA in Labrador Retrievers and people and proposed:
\text{human age} = 16 \ln(\text{dog age}) + 31where ln is the natural logarithm. For a 5-year-old dog: 16 × ln 5 + 31 = 16 × 1.609 + 31 ≈ 57. The formula is based on one breed, so the calculator shows it next to the size chart rather than instead of it.
Life stages
Vets group a dog’s life into stages: puppy (until growth slows, around 6–12 months), young adult (up to about 3), mature adult, and senior for roughly the last quarter of the expected lifespan – from about 10 years for small dogs and 6–7 years for giant breeds. Every dog is different, so ask your vet about your own dog’s health and care.
Frequently asked questions
How old is my dog in human years?
Enter its age and size above. As a rule, the first year equals about 15 human years and the second about 9 more; after that each year adds about 4 to 5 years for small dogs and up to 8 for giant breeds.
Why do big dogs age faster?
Large and giant breeds have shorter lifespans than small dogs, so after the first two years each of their years counts for more human years.
Is a dog year 7 human years?
No. That old rule is too simple – dogs mature much faster in their first two years and then age at different speeds by size.
When is a dog a senior?
Roughly in the last quarter of its expected lifespan: about 10 years for small dogs, 8–9 for medium and large dogs, and 6–7 for giant breeds.
What is the DNA-based dog age formula?
human age = 16 × ln(dog age) + 31, from a 2019 UC San Diego study of Labrador Retrievers. It is shown next to the size chart.