The old rule that one dog year equals seven human years is a myth. The American Veterinary Medical Association puts it plainly: dogs do not age at a rate of seven human years per dog year. Dogs grow up very fast in their first two years, then age more steadily, and larger dogs age faster than small ones. The calculator below shows two ways to compare.
Free calculator
Dog age calculator
- DNA methylation clock (2020 study)
- 57 years
Both are rough comparisons for curiosity and life-stage planning, not a measure of your dog’s health.
Dog years to human years chart
Approximate human-equivalent age by adult size, from the American Kennel Club chart. The medium column matches the AVMA’s own chart.
| Dog age | Small (20 lb or less) | Medium (21–50 lb) | Large (51–100 lb) | Giant (over 100 lb) |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 12 |
| 2 years | 24 | 24 | 24 | 22 |
| 3 years | 28 | 28 | 28 | 31 |
| 4 years | 32 | 32 | 32 | 38 |
| 5 years | 36 | 36 | 36 | 45 |
| 6 years | 40 | 42 | 45 | 49 |
| 7 years | 44 | 47 | 50 | 56 |
| 8 years | 48 | 51 | 55 | 64 |
| 9 years | 52 | 56 | 61 | 71 |
| 10 years | 56 | 60 | 66 | 79 |
| 11 years | 60 | 65 | 72 | 86 |
| 12 years | 64 | 69 | 77 | 93 |
| 13 years | 68 | 74 | 82 | 100 |
| 14 years | 72 | 78 | 88 | 107 |
| 15 years | 76 | 83 | 93 | 114 |
| 16 years | 80 | 87 | 99 | 121 |
The size-based method
The most widely used approach counts a medium-size dog’s first year as about 15 human years and the second as about 9 more. After that, each dog year adds roughly 4 to 7 human years depending on size, with small dogs at the low end and giant breeds at the high end. Giant breeds start a little slower in the first year on the AKC chart but quickly overtake every other size.
These charts are approximations. The AVMA notes that weight, breed, and other factors influence how an individual dog ages.
The DNA methylation clock
In a 2020 study in Cell Systems, researchers compared chemical changes to DNA (methylation) in dogs and humans as they age. In 104 dogs, mostly Labrador retrievers, they found a match described by a simple formula: human age = 16 × ln(dog age) + 31, where ln is the natural logarithm.
The formula captures how quickly puppies mature. An 8-week-old puppy lines up with a human baby of about 9 months, a 1-year-old dog with a 31-year-old adult, and a 12-year-old Labrador with a 70-year-old person. The researchers note it fits young and senior dogs best and is more approximate in between, and that breeds with very different lifespans could follow different curves.
| Dog age | 1 | 2 | 4 | 6 | 8 | 10 | 12 | 14 |
|---|---|---|---|---|---|---|---|---|
| Human years (clock) | 31 | 42 | 53 | 60 | 64 | 68 | 71 | 73 |
When is a dog a senior?
The AVMA describes a dog as senior in roughly the last quarter of its breed’s expected life span. Using AKC data, that is about 8–11 years for small and toy dogs, 8–10 for medium, 8–9 for large, and 6–7 for giant breeds. Senior dogs often need a different veterinary schedule, so this is a useful moment to review the visit schedule and start noting signs of aging.
How long a dog is likely to live varies a lot by breed and face shape. See our guide to how long dogs live, by breed.