Dog age calculator: your dog’s age in human years
In shortThe “multiply by 7” rule is wrong. Dogs age very fast at first: around 1 year old, a dog is roughly a 15-year-old teenager, and at 2 he is about 24. After that, each year counts for 4 to 7 human years depending on size, because large dogs age faster than small ones. Enter his age and size, and the calculator does the rest.
The chart, year by year and by size
| Age | Smallunder 22 lb | Medium22 to 55 lb | Large55 to 100 lb | Giantover 100 lb |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 | 31 |
| 4 years | 32 | 34 | 36 | 38 |
| 5 years | 36 | 39 | 42 | 45 |
| 6 years | 40 | 44 | 48 | 52 |
| 7 years | 44 | 49 | 54 | 59 |
| 8 years | 48 | 54 | 60 | 66 |
| 9 years | 52 | 59 | 66 | 73 |
| 10 years | 56 | 64 | 72 | 80 |
| 11 years | 60 | 69 | 78 | 87 |
| 12 years | 64 | 74 | 84 | 94 |
| 13 years | 68 | 79 | 90 | 101 |
| 14 years | 72 | 84 | 96 | 108 |
| 15 years | 76 | 89 | 102 | 115 |
| 16 years | 80 | 94 | 108 | 122 |
Why the “times 7” rule doesn’t work
It comes from a division: about 70 years of human life expectancy for about 10 years of dog life. But dogs don’t age in a straight line. At 1 year, most dogs are sexually mature and nearly grown, while a 7-year-old child is not. The first year is a sprint, the rest is a trot.
And size changes everything: large and giant dogs age faster and live shorter lives. Across more than half a million dogs in the UK, small breeds lived longer on average than large ones. An 8-year-old Great Dane is already old; a Chihuahua of the same age is often in his prime.
Two ways to calculate, two answers
The rule of thumb many vets use: about 15 human years for the first year, 24 at age 2, then 4 years per year for a small dog, 5 for a medium dog, 6 for a large dog and 7 for a giant. It gives the main result and the chart below.
The epigenetic formula, published in 2020: by comparing the DNA “clock” of Labradors and humans, researchers proposed human age ≈ 16 × ln(dog age) + 31. It makes young dogs older (a 1-year-old Lab would be around 30) and ignores size. Both methods agree on the big picture: dogs age fast early on, then more slowly.
When does a dog become a senior?
The American Animal Hospital Association (AAHA, 2019) places the senior stage in the last quarter of a dog’s expected lifespan rather than at a fixed age. In practice that is around 10 for a small dog, 9 for a medium dog, 8 for a large dog and 7 for a giant, with big differences between individuals.
The signs are often subtle and show up in behavior: he sleeps more, gets up more slowly, tolerates some handling less (joint pain is often why), hears less, or seems lost in the evening, sometimes staring at a wall. None of this is “just old age”: many vets suggest a checkup every six months from that point on.
Frequently asked questions
How old is a 1-year-old dog in human years?
About 15 by the rule of thumb: a teenager, sexually mature, full of energy and still learning. The 2020 epigenetic formula says closer to 30. Both say the same thing: the first year goes very fast.
How old is a 10-year-old dog in human years?
It depends on size: about 56 for a small dog, 64 for a medium dog, 72 for a large dog and 80 for a giant, by the rule of thumb. It is a useful order of magnitude for adjusting his care, not a measured biological age.
Why do small dogs live longer?
Nobody fully knows. Large breeds grow very fast and seem to age faster afterward. Large studies of vet records show that small breeds live longer on average, with big differences between breeds, and that some medium-sized, very flat-faced breeds are more likely to die young.
What about a puppy only a few months old?
Enter his age in months: the calculator follows the fast growth of the first months. Around 6 months, a puppy is roughly a 10-year-old child. It is the age of learning, socialization and big mischief, and the time when habits form fastest.
Sources
The studies this page relies on, with a link to the original publication.
- Wang et al. (2020). Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems.Comparing the epigenetic clocks of Labradors and humans, the authors propose: human age ≈ 16 × ln(dog age) + 31. Dogs age very fast early on, then more slowly.
- Creevy et al. (2019). 2019 AAHA canine life stage guidelines. Journal of the American Animal Hospital Association.Five canine life stages; a dog becomes a senior in the last quarter of his expected lifespan, so earlier in large breeds.
- McMillan et al. (2024). Longevity of companion dog breeds: those at risk from early death. Scientific Reports.Across more than half a million UK dogs, median longevity is about 12.5 years; small breeds and females live longer on average.
- Teng et al. (2022). Life tables of annual life expectancy and mortality for companion dogs in the United Kingdom. Scientific Reports.In the United Kingdom, a puppy’s life expectancy is about 11 years, with wide gaps between breeds.
Mimo reads behavior. It does not replace a vet.