Dog Age Calculator — How Old Is My Dog in Human Years?
This dog age calculator converts your dog's age into human years using current veterinary science, not the outdated multiply by 7 rule. Enter your dog's age and size (small, medium, large, or giant) to see how old your dog really is, plus their life stage and how the new research compares to the old myth.
Choose the size your dog will reach when fully grown. Always use adult size, even for a puppy. A Great Dane puppy is Giant from day one.
How the Dog Age Calculator Works
Enter your dog's age (in years, and months if you know them), then pick the size your dog reaches as a full-grown adult. The calculator returns your dog's age in human years using the size-based chart that vets and the American Kennel Club use.
The size setting always means adult size, not your dog's current weight. A puppy of a large breed is still "large" for this purpose, because aging speed is set by the size a dog grows into. For the first two years every size ages at the same rate, so a young puppy lands on the same number whatever size you pick. The size choice starts to matter from year three onward, which is why it still pays to set it correctly.
Next to the main result you will see two extra numbers. One uses the new epigenetic science (more on that below), and one uses the old "1 dog year is 7 human years" rule, so you can see how far off the myth really is.
Why the 7 Year Rule Is a Myth
The idea that one dog year equals seven human years is one of the most repeated pet facts, and it is wrong. It most likely began in the 1950s as a way to encourage owners to bring pets in for annual checkups, based on the rough idea that people lived to about 70 and dogs to about 10. Vets have debunked it for years (the AVMA is clear that dogs do not age at a flat rate of seven years per year).
The reality is that dogs grow up fast and then slow down. A dog reaches roughly 15 human years by the end of year one, about 24 by the end of year two, and then ages more gradually after that (the exact pace depends on size).
The New Science Behind Dog Years
In 2019, researchers at UC San Diego developed a more accurate formula by studying DNA methylation, the chemical marks that build up on DNA as both dogs and humans age. They found that dogs age on a logarithmic curve (fast early, then gradual), and produced the formula human age = 16 x ln(dog age) + 31. This epigenetic clock research was a clear step up from the 7x myth.
It does have one limit (it was based on Labrador Retrievers only), so it cannot account for size on its own. That is why this tool shows the epigenetic number next to the size-based chart, rather than relying on it alone.
Dog Years to Human Years by Size
Size is the single biggest factor in how fast a dog ages, because body mass is closely tied to lifespan. Smaller dogs tend to live longer and age more slowly, while large and giant breeds age faster. After the first two years, each extra year adds about 4 human years for a small dog, 5 for a medium dog, 6 for a large dog, and 7 for a giant breed. So a 10 year old small dog is around 56 in human years, while a 10 year old giant breed is closer to 80.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 29 | 30 | 31 |
| 4 | 32 | 34 | 36 | 38 |
| 5 | 36 | 39 | 42 | 45 |
| 6 | 40 | 44 | 48 | 52 |
| 7 | 44 | 49 | 54 | 59 |
| 8 | 48 | 54 | 60 | 66 |
| 9 | 52 | 59 | 66 | 73 |
| 10 | 56 | 64 | 72 | 80 |
| 11 | 60 | 69 | 78 | 87 |
| 12 | 64 | 74 | 84 | 94 |
| 13 | 68 | 79 | 90 | 101 |
| 14 | 72 | 84 | 96 | 108 |
| 15 | 76 | 89 | 102 | 115 |
| 16 | 80 | 94 | 108 | 122 |
Prefer to scan the numbers without the tool? See the standalone dog age chart or the quick dog years to human years converter.
When Is My Dog a Senior?
Senior age also depends on size. Small dogs are often considered senior around 10, medium dogs at 8 to 10, large dogs at 6 to 8, and giant breeds as early as 5 to 6. This is why a large or giant dog may need senior-stage care (diet, joint support, more frequent checkups) at an age when a small dog is still middle-aged. Ongoing work such as the Dog Aging Project continues to refine how we understand canine aging. For more date and time tools, see our other free calculators.
Frequently Asked Questions
It depends on age and size. A common guide is 15 human years for the first year, 9 more for the second (24 total), then about 4 to 7 per year after that depending on size. Enter your dog’s details in the calculator above for a specific estimate.
No. The 7x rule is a myth that likely began as a vet-visit marketing message in the 1950s. Dogs age quickly in their first two years and then more slowly, so a flat multiplier does not reflect how they really age.
Always pick the size your dog will be as a full-grown adult, not its current puppy size. A Great Dane puppy is Giant, and a Chihuahua puppy is Small. For the first two years the result is the same whatever size you choose, so there is no harm in setting it early, and it keeps the answer accurate as your dog grows.
Mostly through size. The science is driven by size band (a stand-in for body mass) rather than individual breed, so two breeds of the same adult size age at a similar rate. Choosing your dog’s adult size gives you an accurate estimate.
Count the first year as 15, the second as 9 more (24 total), then add 4 (small), 5 (medium), 6 (large), or 7 (giant) for each year after that. The calculator does this for you, including partial years.
A 2019 UC San Diego study produced human age = 16 x ln(dog age) + 31, based on DNA methylation (the "epigenetic clock"). It is more accurate than the 7x rule, though it was based on one breed, so we show it alongside the size-based chart.
It varies by size. Small dogs are often senior around 10, medium dogs at 8 to 10, large dogs at 6 to 8, and giant breeds as early as 5 to 6 years.