How Old Is My Dog in Human Years?
Enter your dog's age and adult size above to convert dog years to human years. Size matters because big dogs age faster than small ones: a 10-year-old Chihuahua is middle-aged, while a 10-year-old Great Dane is very elderly. The calculator uses the widely used veterinary size chart below and fills in the months between whole years.
Is One Dog Year Really Seven Human Years?
No. The old rule of multiplying by seven is a myth. Dogs grow up very quickly. Most reach adulthood within their first year, which is roughly like a 15-year-old human. By age two a dog is about 24 in human terms. After that, each dog year adds about 4 to 7 human years depending on size, with small breeds aging slowest and giant breeds fastest.
Dog Age Chart by Size
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 107 |
| 15 | 76 | 83 | 93 | 114 |
| 16 | 80 | 87 | 99 | 121 |
Small: up to 20 lb. Medium: 21–50 lb. Large: 51–100 lb. Giant: over 100 lb. Figures are approximate human-equivalent ages.
The DNA Method
In 2020, researchers at the University of California San Diego compared age-related chemical changes in the DNA of Labrador Retrievers and humans. They proposed the formula human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. It suggests dogs age extremely fast early on, so a 1-year-old Labrador is like a 31-year-old human, and slow down later. It was built from one breed, so the calculator shows it as a second estimate alongside the size chart.
Dog Life Stages
- Puppy: birth to about 1 year (up to 18–24 months for giant breeds).
- Young adult: about 1 to 3 years, fully grown and full of energy.
- Mature adult: from about 3 years until the senior years.
- Senior: roughly the last quarter of expected lifespan. That is about 6 to 7 years for giant breeds, 8 for large, 10 for medium and 11 for small dogs.
Senior dogs benefit from twice-yearly vet checkups. Ask your vet what is normal for your dog's breed.