Want the answer for your own dog? Use the pet age calculator — it handles months and in-between ages too.
Why the 7× rule is wrong
Dogs don't age at a constant rate. A one-year-old dog is roughly a young adult — about 15 human years, not 7 — and a two-year-old is around 24. After that, aging slows to roughly 4–7 human years per calendar year, and size starts to matter: small dogs age slowest and giant breeds fastest. The American Veterinary Medical Association's rule of thumb (via the AKC) for a medium dog: 15 human years for year one, about 9 for year two, about 5 for each year after.
Dog age chart by size
Anchor rows (ages 1, 2, 3, 5, 7, 10, 15, 20) are from the American Animal Hospital Association's age chart (PDF); the rows between them are our linear interpolation of those published values, rounded to the nearest year. No published value exists for a 20-year-old giant breed, so those last giant rows extend the chart's final trend.
| Dog age | Small ≤20 lb | Medium 21–50 lb | Large 51–90 lb | Giant 90+ lb |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 28 | 30 | 32 |
| 4 | 32 | 33 | 35 | 37 |
| 5 | 36 | 37 | 40 | 42 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 63 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 78 |
| 11 | 60 | 65 | 71 | 85 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 108 |
| 15 | 76 | 83 | 93 | 115 |
| 16 | 80 | 87 | 98 | 122 |
| 17 | 84 | 92 | 104 | 130 |
| 18 | 88 | 96 | 109 | 137 |
| 19 | 92 | 101 | 115 | 145 |
| 20 | 96 | 105 | 120 | 152 |
The epigenetic clock (the science-y version)
A 2019 UC San Diego study compared DNA methylation in dogs and humans and fit the formula human age = 16 × ln(dog age) + 31. It says dogs age extremely fast early (a 1-year-old maps to ~31 human years) and slowly later. The cohort was Labrador Retrievers only, so it may not transfer to other breeds — our calculator shows it alongside the chart value for comparison.
When is a dog a senior?
Per the AVMA, small dogs are typically considered senior from about age 7, and larger breeds from 5–6 — earlier because bigger dogs age faster and have shorter average lifespans. Senior status is a checkup-frequency signal, not a countdown.
Also: cat years to human years.