Dogs
Dog age calculator: dog years to human years
A dog’s first year equals about 15 human years and its second about 9 more; after that each year adds 4 to 7, more for bigger dogs. A 7-year-old medium dog is about 47.
Dog years to human years chart
Each row is one dog year. Small is up to 20 lb, medium 21–50 lb, large 51–90 lb and giant over 90 lb. Years 1–16 are the published size chart; 17–20 continue it at each size’s last yearly step. The last column is the 2020 DNA formula.
| Dog age | Small | Medium | Large | Giant | DNA formula |
|---|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 | 31 |
| 2 | 24 | 24 | 24 | 24 | 42 |
| 3 | 28 | 28 | 30 | 32 | 49 |
| 4 | 32 | 33 | 35 | 37 | 53 |
| 5 | 36 | 37 | 40 | 42 | 57 |
| 6 | 40 | 42 | 45 | 49 | 60 |
| 7 | 44 | 47 | 50 | 56 | 62 |
| 8 | 48 | 51 | 55 | 64 | 64 |
| 9 | 52 | 56 | 61 | 71 | 66 |
| 10 | 56 | 60 | 66 | 78 | 68 |
| 11 | 60 | 65 | 72 | 86 | 69 |
| 12 | 64 | 69 | 77 | 93 | 71 |
| 13 | 68 | 74 | 82 | 101 | 72 |
| 14 | 72 | 78 | 88 | 108 | 73 |
| 15 | 76 | 83 | 93 | 115 | 74 |
| 16 | 80 | 87 | 99 | 123 | 75 |
| 17 | 84 | 92 | 104 | 130 | 76 |
| 18 | 88 | 96 | 110 | 138 | 77 |
| 19 | 92 | 100 | 116 | 146 | 78 |
| 20 | 96 | 105 | 121 | 153 | 79 |
Citing this? Link to https://tools.thesturdypaw.com/dog-age/. Chart computed by our calculator from the size-based figures US vets publish. Free to reuse with a link (CC BY 4.0).
How the dog age calculator works
It reads your dog’s age off the size-based chart that US vet groups publish, which starts every dog at 15 human years for the first year and 24 at two, then adds 4 to 7 human years a year depending on size. Between whole years it interpolates, so 5 years and 6 months lands halfway between 5 and 6.
It also shows the 2020 epigenetic formula, human age = 16 × ln(dog age) + 31, which researchers at UC San Diego derived from DNA changes in 104 Labrador retrievers. That formula makes young dogs “older” fast and slows down later, so the two methods disagree most at the ends.
Questions
Is one dog year equal to seven human years?
No: the “times seven” rule is a myth. A dog’s first year is worth about 15 human years and its second about 9 more, so a 2-year-old dog is roughly 24. After that each year adds about 4 to 7 human years, depending on size.
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 breed, using the size-based chart.
How old is a 7-year-old dog in human years?
About 47 for a medium-sized dog (21–50 lb); small dogs are a little younger and giant breeds older, as the chart above shows.
Why do big dogs age faster?
Large and giant breeds have shorter lifespans than small dogs, so each year after the second counts for more human years on the chart: about 4 for small dogs and 7 or more for giants.
What is the DNA formula for dog age?
It’s human age = 16 × ln(dog age) + 31, from a 2020 study in Cell Systems that compared age-related DNA changes in 104 Labrador retrievers with those in people. It was built on one breed, so treat it as a second opinion.
When is my dog a senior?
AAHA’s life stage guidelines define a senior dog as one in the last quarter of its breed’s expected lifespan, which comes earlier for large and giant breeds. Your vet can tell you when to start senior check-ups.
How old is a 5-year-old dog in human years?
About 36 for a small dog, 37 for a medium dog and 40 for a large one.
How old is a 13-year-old dog in human years?
About 68 if it is small, 74 if medium and 82 if large; few giant breeds reach 13.
How old is a 1-year-old dog in human years?
About 15, roughly a teenager: most dogs are physically mature at one, even if they still act young.
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