Human years to dog years
Want it the other way round? The second calculator converts a human age into the equivalent dog age for each size. Because large dogs age faster, the same human age corresponds to a younger dog in big breeds.
| Human age | Small dog | Medium dog | Large dog | Giant dog |
|---|---|---|---|---|
| 20 years | 1.6 yrs | 1.6 yrs | 1.6 yrs | 1.8 yrs |
| 30 years | 3.5 yrs | 3.5 yrs | 3.5 yrs | 2.9 yrs |
| 40 years | 6 yrs | 5.7 yrs | 5.4 yrs | 4.3 yrs |
| 50 years | 8.5 yrs | 7.7 yrs | 7 yrs | 6.1 yrs |
| 60 years | 11 yrs | 10 yrs | 8.8 yrs | 7.5 yrs |
| 70 years | 13.5 yrs | 12.2 yrs | 10.7 yrs | 8.9 yrs |
| 80 years | 16 yrs | 14.4 yrs | 12.6 yrs | 10.1 yrs |
Why "1 dog year = 7 human years" is wrong
Dogs mature far faster than people early in life: a one-year-old dog is roughly as developed as a 15-year-old human, and a two-year-old is about 24. After that, aging slows, but at different speeds by size. Small dogs age about 4 human years per year, while giant breeds can age 7-8 or more.
Dog years to human years chart
Size categories: small up to 20 lb, medium 21-50 lb, large 51-100 lb, giant over 100 lb. This is the size-based chart commonly used by veterinarians.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 12 |
| 2 years | 24 | 24 | 24 | 22 |
| 3 years | 28 | 28 | 28 | 31 |
| 4 years | 32 | 32 | 32 | 38 |
| 5 years | 36 | 36 | 36 | 45 |
| 6 years | 40 | 42 | 45 | 49 |
| 7 years | 44 | 47 | 50 | 56 |
| 8 years | 48 | 51 | 55 | 64 |
| 9 years | 52 | 56 | 61 | 71 |
| 10 years | 56 | 60 | 66 | 79 |
| 11 years | 60 | 65 | 72 | 86 |
| 12 years | 64 | 69 | 77 | 93 |
| 13 years | 68 | 74 | 82 | 100 |
| 14 years | 72 | 78 | 88 | 107 |
| 15 years | 76 | 83 | 93 | 114 |
| 16 years | 80 | 87 | 99 | 121 |
The DNA-based formula
A 2020 study from UC San Diego compared DNA methylation (an "epigenetic clock") in Labrador retrievers and humans and proposed human age = 16 × ln(dog age) + 31. It suggests dogs age very rapidly in the first year. Under this formula a 1-year-old is about 31 and a 10-year-old about 68. The study used one breed only, so we show it alongside the size-based chart.
| Dog age | Human-age equivalent (DNA clock) |
|---|---|
| 1 | 31 |
| 2 | 42 |
| 3 | 49 |
| 4 | 53 |
| 5 | 57 |
| 6 | 60 |
| 8 | 64 |
| 10 | 68 |
| 12 | 71 |
| 14 | 73 |
| 16 | 75 |
Dog life stages
- Puppy: birth to about 1 year (up to 18-24 months in giant breeds).
- Young adult: about 1-3 years.
- Mature adult: from about 3 years until senior.
- Senior: around 7 years for giant breeds, 8 for large, 10 for medium and 11 for small dogs.
Senior dogs benefit from twice-yearly vet checkups, bloodwork and attention to weight, joints and teeth. Older dogs often need fewer calories. Recheck portions with the dog food calculator.
Frequently asked questions
How old is a 7-year-old dog in human years?
About 44 for a small dog, 47 for medium, 50 for large and 56 for giant breeds, using the size-based veterinary chart.
How old is a 1-year-old dog in human years?
Roughly 15 human years for most dogs, about 12 for giant breeds, which mature more slowly at first.
Why do big dogs age faster?
Large dogs grow quickly and appear to age faster in adulthood, which is reflected in their shorter average lifespans. The exact biology is still being researched.
What age is a senior dog?
Commonly around 7 years for giant breeds and 10-11 years for small dogs. Your vet may recommend senior screening earlier.