1 year in dog years is about 15 human years
A 1-year-old dog is about 15 in human years if it is medium-sized (21 to 50 lb), on AVMA’s chart. A small dog of the same age is about 15, a large one 15 and a giant one 15. The DNA clock of a 2020 study gives 31.0.
1 year in human years, by size
| Size | Human years | Life stage (AAHA) | Senior from (VCA) |
|---|---|---|---|
| Small (20 lb or less) | 15 | Young adult | 11 years |
| Medium (21 to 50 lb) | 15 | Young adult | 10 years |
| Large (51 to 100 lb) | 15 | Young adult | 8 years |
| Giant (over 100 lb) | 15 | Young adult | 7 years |
Dog age calculator, with 1 year filled in: change the size, or work a human age back to dog years.
The first year is the fastest
How many dog years is one human year? At the start, about 15: AVMA’s chart and Merck’s table both put a dog of 1 at 15 human years. Merck’s table gives 10 to 15 human years for 6 to 12 months.
AAHA ends the puppy stage when rapid growth stops, at about 6 to 9 months, and says that point varies with breed and size. Most 1-year-olds are young adults by that definition.
This is where the sources disagree the most. The DNA clock of Wang et al. puts a 1-year-old at 31: the study found the methylome of puppies changing much faster than that of children, and it matched a puppy of about 8 weeks with a baby of about 9 months, the age both grow their first teeth.
What changes in the first year
A dog goes from birth to about 15 human years on the charts, whatever its size: the charts only part ways after the second birthday. The DNA clock puts the end of the first year at 31.
Life stage at 1
Dogs of every size are young adults at 1, by the stages of the 2019 AAHA guidelines and the senior ages of VCA (small 11, medium 10, large 8, giant 7).
No size turns senior at exactly 1.
What the DNA clock says about a 1-year-old dog
Wang et al. (Cell Systems, 2020) matched the DNA methylation of 104 Labrador retrievers with that of people and fitted human age = 16 × ln(dog age) + 31. For 1 year that is 31.0 human years, 16.0 more than the 15 of AVMA’s chart for a medium dog.
At 1, the clock reads older than the chart of every size: it ages young dogs much faster than the charts do.
The seven-year rule at this age
Seven times 1 is 7. The chart puts a 1-year-old dog between 15 and 15 human years by size, and the medium dog at 15, so the rule is 8 human years too low for a medium dog. No veterinary source on this page uses it.
Frequently asked questions
How old is a 1-year-old dog in human years?
About 15 for a small dog (20 lb or less), 15 for a medium dog (21 to 50 lb), 15 for a large dog (51 to 100 lb) and 15 for a giant dog (over 100 lb), on the charts of AVMA, Merck and PetMD. Your veterinarian can tell you where your own dog is.
Is a 1-year-old dog a senior?
Not by size alone: VCA counts dogs as seniors from 7 (giant) to 11 or 12 (small), so a 1-year-old of any size is not there yet. AAHA defines a senior as a dog in the last 25% of its expected life.
Other ages in dog years
Dog age chart: every age and size in one table · Dog age calculator
Sources
- AVMA, Pets age faster than people (chart for a medium-sized dog of 21 to 50 lb)
- Merck Veterinary Manual, Description of Dogs (Antinoff, reviewed October 2026), Dog years versus human years
- PetMD, How Old Is My Dog in Human Years? (Coates, DVM, December 2024)
- Wang T, et al. Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome. Cell Systems 2020;11(2):176–185
- The same study, free full text on PubMed Central (PMC7484147)
- 2019 AAHA Canine Life Stage Guidelines (Creevy et al., JAAHA 2019;55:267–290), Table 1
- VCA Animal Hospitals, How Old is Old? Comparing Dog Age to Human Age (Weir, Llera, Buzhardt)