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Dog age calculator
Find out how old your dog is in human years. Bigger dogs age faster, so the calculator uses your dog's size.
Your dog's age in human years and the full chart for its size will show here.
Age comparisons are approximate and vary by breed and health. Last reviewed October 6, 2026.
Why "multiply by 7" is wrong
The old rule that one dog year equals seven human years doesn't match how dogs grow. Dogs mature very fast at first: a one-year-old dog is roughly like a 15-year-old person. After that, aging slows down, and how fast it continues depends on size.
The American Veterinary Medical Association sums it up as 15 human years for the first year of a medium-sized dog, about 9 more for the second year, and then roughly 5 human years for each year after. Large and giant breeds age faster in later life, which is why they are often considered senior earlier: around 5 to 6 years for large breeds, compared with about 7 for small dogs.
Dog years to human years chart
This is the size-based chart from the American Animal Hospital Association that the calculator uses. Ages between whole years are interpolated.
| Dog age | Small ≤20 lb | Medium 21–50 lb | Large 51–90 lb | Giant >90 lb |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 28 | 30 | 32 |
| 4 | 32 | 33 | 35 | 37 |
| 5 | 36 | 37 | 40 | 42 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 78 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 101 |
| 14 | 72 | 78 | 88 | 108 |
| 15 | 76 | 83 | 93 | 115 |
| 16 | 80 | 87 | 99 | 123 |
The epigenetic formula
In 2020, researchers at the University of California San Diego compared chemical changes in DNA as dogs and people age. They proposed this formula:
Human age = 16 × ln(dog age) + 31
"ln" is the natural logarithm. By this formula a 1-year-old dog is like a 31-year-old person, a 4-year-old like a 53-year-old, and a 10-year-old like a 68-year-old. The study used only Labrador Retrievers, so the calculator shows it as a second opinion next to the size-based chart.
Questions people ask
How old is my dog in human years?
For most dogs, the first year equals about 15 human years and the second year about 9 more, so a 2-year-old dog is roughly 24 in human years. After that, small dogs add about 4 human years per year and giant dogs up to about 7 or 8. Enter your dog's age and size above for an exact figure from the chart.
Is 1 dog year really 7 human years?
No. That rule is a myth that ignores how fast puppies mature and how much size matters. A 1-year-old dog is closer to a 15-year-old person than to a 7-year-old.
Why do big dogs age faster than small dogs?
Large and giant breeds tend to have shorter lifespans, so each year of their adult life is a bigger share of their total life. That is why the chart adds more human years per dog year as size goes up, especially after about age 5.
When is a dog considered a senior?
It depends on size. Small dogs are generally considered senior at around 7 years, while large-breed dogs are often considered senior at 5 to 6 years.
How old is a 6-month-old puppy in human years?
The chart starts at 1 year, so for puppies the calculator scales the first year evenly: a 6-month-old puppy comes out at about 7 to 8 human years. Puppies develop unevenly, so treat this as a rough guide.
Can I convert my age into dog years?
Yes. Switch the calculator to "Human → dog years", enter an age and pick a size. It reverses the chart to show the dog age that matches.