Life stage
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Life stages depend on age and size.
- Usually senior from
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- Old “×7” rule says
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Dog Age Calculator
Enter your dog’s age and size to see it in human years two ways: with a DNA-based formula and a size-adjusted rule of thumb.
In human years
–by DNA science
–by size
Enter your dog’s age to convert it to human years.
Every method compared
- DNA methylation clock
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- Small dog
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- Medium dog
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- Large dog
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- Giant dog
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All values are estimates in human years. How each method works
Why “multiply by seven” doesn’t work
The old idea that one dog year equals seven human years makes a 1-year-old dog the equivalent of a 7-year-old child. In reality most dogs are physically mature by their first birthday, much more like a teenager. Dogs race through puppyhood and adolescence, then age more steadily, and size changes the pace: a Great Dane is elderly at an age when a Chihuahua is middle-aged.
That’s why this calculator gives you two better estimates side by side.
How the two methods work
The DNA formula (epigenetic clock)
In 2020, researchers at the University of California San Diego published a study in the journal Cell Systems comparing chemical marks on DNA, called methylation, in 104 Labrador retrievers with the same marks in humans. These marks change with age in a predictable way, so they work like a clock. Matching the dog and human clocks gave a formula:
Human age = 16 × ln(dog’s age) + 31, where ln is the natural logarithm.
The curve is steep early on. A 1-year-old dog comes out at about 31 human years, a 4-year-old at about 53, and then it flattens: a 12-year-old is about 71. The formula comes from a single breed, so it doesn’t account for size, and it isn’t meaningful for very young puppies (the calculator shows it from 2 months old).
The size-adjusted rule of thumb
A widely quoted guideline from the American Veterinary Medical Association counts a medium-sized dog’s first year as about 15 human years, the second year as about nine more, and each year after that as about four or five more (AKC). Because bigger dogs age faster after maturity, we extend it by size: after the second birthday we add 4 years a year for small dogs (up to 9 kg or 20 lb), 5 for medium (up to 23 kg or 50 lb), 6 for large (up to 45 kg or 100 lb) and 7 for giant breeds. It’s a simplification, but it captures the size effect that the DNA formula misses.
Dog years compared
The two methods tell different stories. The DNA formula puts more of a dog’s aging into its first few years, while the size rule keeps adding years steadily and separates small dogs from big ones.
| Dog age | DNA formula | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 1 year | 31 | 15 | 15 | 15 | 15 |
| 2 years | 42 | 24 | 24 | 24 | 24 |
| 3 years | 49 | 28 | 29 | 30 | 31 |
| 4 years | 53 | 32 | 34 | 36 | 38 |
| 5 years | 57 | 36 | 39 | 42 | 45 |
| 6 years | 60 | 40 | 44 | 48 | 52 |
| 7 years | 62 | 44 | 49 | 54 | 59 |
| 8 years | 64 | 48 | 54 | 60 | 66 |
| 9 years | 66 | 52 | 59 | 66 | 73 |
| 10 years | 68 | 56 | 64 | 72 | 80 |
| 11 years | 69 | 60 | 69 | 78 | 87 |
| 12 years | 71 | 64 | 74 | 84 | 94 |
| 13 years | 72 | 68 | 79 | 90 | 101 |
| 14 years | 73 | 72 | 84 | 96 | 108 |
| 15 years | 74 | 76 | 89 | 102 | 115 |
| 16 years | 75 | 80 | 94 | 108 | 122 |
Your dog’s life stage
The calculator also shows a simplified life stage. The American Animal Hospital Association’s canine guidelines describe puppy, young adult, mature adult and senior stages, plus an end-of-life stage that can come at any age. The age at which a dog becomes senior depends heavily on size: larger breeds are often considered senior at around 5 to 6 years old, smaller dogs at about 7. Knowing the stage helps you and your vet plan diet, exercise and check-ups.
Which number should I use?
Use both as a rough guide, not a diagnosis. If your dog is a large or giant breed, the size-adjusted rule is probably the better day-to-day guide, because the DNA formula was built from a single medium-to-large breed. Neither method knows about your dog’s health, weight or genetics, and two dogs of the same age and size can age very differently. Your vet is the best judge of how old your dog really is in body.
Read more about the science, including how the study was done, in our guide to dog years and human years. Have a cat as well? Try the cat age calculator.
Last reviewed on by the Ageculator Team. See how we calculate.
Frequently asked questions
How old is my dog in human years?
Enter your dog’s age and size above. You’ll get two estimates: one from a formula based on changes in dogs’ DNA, and one from the size-adjusted rule of thumb many vets use. Neither is exact, so treat both as a guide to your dog’s life stage rather than a precise number.
Is one dog year really seven human years?
No. Dogs grow up far faster than that at the start: most are adults by their first birthday, which is more like a human 15 than a human 7. After that they age more slowly, and big dogs age faster than small ones.
How old is a 10-year-old dog in human years?
About 68 by the DNA-based formula. By the size rule it ranges from about 56 for a small dog to about 80 for a giant breed, with medium dogs around 64.
Why do large dogs age faster than small ones?
Big breeds grow very fast and tend to have shorter lifespans, so they reach their senior years sooner. Many giant breeds count as seniors by about 5 or 6 years old, while small dogs often don’t until about 7 or later.
When is a dog considered a senior?
It depends on size. The usual guide is about 7 years for small and medium dogs, around 6 for large dogs and 5 or 6 for giant breeds. Your vet can tell you when to start senior check-ups for your dog.