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Dog age calculator
Convert your dog's age to human years. Bigger dogs age faster, so pick your dog's adult size.
How the calculator works
Dogs age fastest in their first two years. By their first birthday most dogs are about as grown up as a 15-year-old person, and by two they're roughly 24. After that, the pace depends on size. A small dog adds about 4 human years for each year it lives. A giant dog adds 7 or more, because big dogs age faster and tend to have shorter lives.
The calculator uses the dog age chart in the American Animal Hospital Association's (AAHA) life stage guidelines. It picks the column for your dog's adult weight and fills in between birthdays for part years.
Dog age chart
Human-equivalent age by adult weight.
| Dog age | Small20 lb or less | Medium21 to 50 lb | Large51 to 90 lb | Giantover 90 lb |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 28 | 30 | 32 |
| 4 years | 32 | 33 | 35 | 37 |
| 5 years | 36 | 37 | 40 | 42 |
| 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 | 78 |
| 11 years | 60 | 65 | 72 | 86 |
| 12 years | 64 | 69 | 77 | 93 |
| 13 years | 68 | 74 | 82 | 101 |
| 14 years | 72 | 78 | 88 | 108 |
| 15 years | 76 | 83 | 93 | 115 |
| 16 years | 80 | 87 | 99 | 123 |
| 17 years | 84 | 92 | 104 | – |
| 18 years | 88 | 96 | 109 | – |
| 19 years | 92 | 101 | 115 | – |
| 20 years | 96 | 105 | 120 | – |
Source: AAHA canine and feline age chart, adapted from the Dog Owner’s Home Veterinary Handbook. The chart stops at 16 for giant dogs.
Is one dog year really seven human years?
No. The “multiply by seven” rule gets the first two years badly wrong. A one-year-old dog can usually breed and is fully grown or close to it, which is nothing like a seven-year-old child. Seven also doesn't allow for size: a 12-year-old Chihuahua and a 12-year-old Great Dane are at very different points in their lives.
The DNA-based formula
In 2020, researchers at the University of California San Diego compared chemical tags on DNA (methylation) that change with age in dogs and in people. Their formula is human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. It was built from 104 dogs, almost all Labrador Retrievers, so it suits medium and large dogs best. It runs ahead of the chart in early life (a one-year-old comes out at 31) and comes close to it later on: both put a 12-year-old Labrador at about 70 to 77.
The calculator shows the chart figure first, because it covers every size, and the DNA figure underneath for comparison.
Life stages
AAHA's 2019 guidelines group a dog's life into stages that matter more for care than an exact human age:
- Puppy: birth until rapid growth stops, around 6 to 9 months depending on breed and size.
- Young adult: until the dog has finished maturing physically and socially, by 3 to 4 years in most dogs.
- Mature adult: from then until the last quarter of the dog's expected lifespan.
- Senior: the last quarter of expected lifespan. This comes sooner in large and giant breeds, so ask your vet when your dog reaches it.
Not sure how old your dog is? A vet can estimate it from the teeth, eyes and coat, which is usually close for young dogs and rougher for older ones.
Common questions
How old is a 1-year-old dog in human years?
About 15. Dogs do most of their growing up in the first year, so a one-year-old is closer to a teenager than a child.
How old is a 5-year-old dog in human years?
About 36 for a small dog, 37 for a medium dog, 40 for a large dog and 42 for a giant dog.
How old is a 10-year-old dog in human years?
About 56 for a small dog, 60 for a medium dog, 66 for a large dog and 78 for a giant dog.
How old is a 15-year-old dog in human years?
About 76 for a small dog, 83 for a medium dog and 93 for a large dog. Few giant dogs reach 15; on the chart one would be about 115.
Why do big dogs age faster?
Nobody knows for certain. Large and giant breeds grow very fast and have shorter average lifespans, and their bodies show the signs of aging earlier. That's why the chart has a separate column for each size.
Have a cat too? Try the cat age calculator.
Sources: American Animal Hospital Association, 2019 Canine Life Stage Guidelines and its dog age chart. Wang T et al. (2020), “Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome”, Cell Systems 11: 176–185 (doi:10.1016/j.cels.2020.06.006). An estimate, not veterinary advice.