How old is a 3-year-old dog in human years?
A 3-year-old dog is about 28 in human years on the AVMA chart for a medium-size dog (21 to 50 lb), and about 49 by the 2020 DNA-clock formula.
- Age
- 3 years
- Size
- Medium, 20 to 50 lb
The DNA clock reads 21 years higher because its curve counts a dog's first year as about 31 human years and rises fastest in the early years, while the AVMA chart starts at 15 and adds 4 to 6 years a year.
Life stage
- Puppy
- Young adult (this stage)
- Mature adult (moving into this stage)
- Senior
Medium dogs are senior from about 8 to 10 years (AVMA; stages from AAHA). At this age a dog is moving from young adult to mature adult.
The card shows a medium-size dog. For months or another size, use the dog age calculator.
A 3-year-old dog by size
AVMA publishes a year-by-year human age only for medium dogs. What size does change is when a dog becomes a senior, so here is the life stage at 3 years for each AVMA size group.
| Size and adult weight | Life stage at 3 years | Senior from (years) |
|---|---|---|
| Small or toyless than 20 lb | Young adult or mature | 8 to 11 |
| Medium20 to 50 lb | Young adult or mature | 8 to 10 |
| Large50 to 90 lb | Young adult or mature | 8 to 9 |
| Giantmore than 90 lb | Young adult or mature | 6 to 7 |
The math
AVMA chart, 3 years: 28 human yearsThe chart goes 24 at 2 years, 28 at 3, 32 at 4.
DNA clock: 16 × ln(3) + 31 = 16 × 1.099 + 31 = 48.6ln is the natural logarithm. Rounded, that is 49 human years.
The formula comes from DNA methylation in Labrador retrievers; its authors say breeds with longer or shorter lives could follow a different curve.
Nearby ages
| Dog age | AVMA chart (medium) | DNA clock | Times 7 |
|---|---|---|---|
| 1 year | 15 | 31 | |
| 2 years | 24 | 42 | |
| 3 years | 28 | 49 | |
| 4 years | 32 | 53 | |
| 5 years | 36 | 57 | |
| 6 years | 42 | 60 | |
| 7 years | 47 | 62 |
See all ages in the dog years chart, or compare a 3-year-old cat.
Sources
- AVMA, “Pets age faster than people” (PDF). Dog column for a medium-size dog of 21 to 50 lb, ages 1 to 16; cat column, ages 1 to 16. AVMA adds that pet ages are approximate and that weight and breed may influence aging.
- AVMA, “Caring for senior cats and dogs.” Dog size groups by weight, the age each group becomes senior, cats senior after about 10, and the statement that dogs don’t age 7 human years per year.
- AVMA “Senior Pets” client brochure, revision 7/10, since replaced by a 2023 edition without the chart (archived copy). Human-age ranges from small to very large dogs at 7, 10, 15 and 20 years.
- Wang T, Ma J, Hogan AN, et al. “Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome.” Cell Systems 11 (2020). The formula human age = 16 ln(dog age) + 31, from 104 dogs, mostly Labrador retrievers, aged a few weeks to 16 years. See also the UC San Diego news release.
- UC Davis School of Veterinary Medicine, “Calculating your dog’s age.” Why the times-7 rule is inaccurate and where it likely came from.
- 2019 AAHA Canine Life Stage Guidelines (PDF). Puppy, young adult, mature adult, senior and end-of-life stages.