15 years in dog years is about 83 human years
A 15-year-old dog is about 83 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 76, a large one 95.5 and a giant one 121.5. The DNA clock of a 2020 study gives 74.3.
15 years in human years, by size
| Size | Human years | Life stage (AAHA) | Senior from (VCA) |
|---|---|---|---|
| Small (20 lb or less) | 76 | Senior | 11 years |
| Medium (21 to 50 lb) | 83 | Senior | 10 years |
| Large (51 to 100 lb) | 95.5 | Senior | 8 years |
| Giant (over 100 lb) | 121.5 | Senior | 7 years |
Dog age calculator, with 15 years filled in: change the size, or work a human age back to dog years.
Every chart is above the DNA clock
Merck’s last row lists 15 to 20 dog years as 76 to 96 human years, four a year. A small dog of 15 is 76 on this page’s chart, now above the clock’s 74.3; every size reads older than the clock from here.
The clock adds about one human year a year at this age, against four to seven and a half on the size charts: the two approaches agree least about old dogs and young puppies.
What changes from 14 to 15
This birthday adds 4 for a small dog, 5 for a medium dog, 5.5 for a large dog and 7.5 for a giant dog in human years on the chart. The DNA clock adds 1.1.
Life stage at 15
Dogs of every size are seniors at 15, 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 15.
What the DNA clock says about a 15-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 15 years that is 74.3 human years, 8.7 fewer than the 83 of AVMA’s chart for a medium dog.
At 15, the chart of every size reads at least the clock: the clock slows down in later life, while the charts keep adding several human years a year.
The seven-year rule at this age
Seven times 15 is 105. The chart puts a 15-year-old dog between 76 and 121.5 human years by size, and the medium dog at 83, so the rule is 22 human years too high for a medium dog. No veterinary source on this page uses it.
Frequently asked questions
How old is a 15-year-old dog in human years?
About 76 for a small dog (20 lb or less), 83 for a medium dog (21 to 50 lb), 95.5 for a large dog (51 to 100 lb) and 121.5 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 15-year-old dog a senior?
Yes, whatever its size: VCA counts dogs as seniors from 7 (giant) to 11 or 12 (small). AAHA defines a senior as a dog in the last 25% of its expected life and suggests exams at least every six months.
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)