Medium dog, 5 years
About 36 human years on the chart; 57 with the UCSD formula.
Dog age calculator
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Uses the size-based chart vets commonly share, after AVMA guidance: the first year of a dog's life is about 15 human years, the second adds about 9, and bigger breeds age faster after that. A second figure uses the 2020 UCSD formula, 16 × ln(dog age) + 31, which was built from Labrador retrievers.
Size when grown
years
In human years
36
A medium dog aged 5.0 is roughly like a person of 36: adult. The UCSD formula gives 57, because it ages dogs faster early on.
- Life stage
- Adult
- UCSD formula
- 57
- Old 7 × rule
- 35
Size chart36
UCSD formula57
7 × rule35
Dog years to human years by size
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 107 |
| 15 | 76 | 83 | 93 | 114 |
| 16 | 80 | 87 | 99 | 121 |
Why dog years are not just times seven
Dogs grow up fast. By their first birthday most can have puppies and are near full size, which is more like a human teenager than a seven-year-old. So the chart vets use counts the first year as about 15 human years and the second as about 9 more.
After that, size takes over. A medium dog of 5 is about 36 in human terms. At 10, a medium dog is about 60 but a large dog is about 66, and a giant breed about 79. That matches how long they tend to live.
In 2020 researchers at UC San Diego compared DNA changes in dogs and people and came up with 16 × ln(age) + 31. It ages dogs very quickly at first: a 5-year-old works out at about 57. It was built from Labradors, so treat it as a second opinion rather than a rule.
Whichever number you use, the practical point is the same. Once your dog reaches the senior range, more frequent vet checks help catch problems with joints, teeth, kidneys and weight early.
Sources
What this calculator does not account for
- Breed differences within a size group.
- The dog's own health and weight.
- Puppies under a year in the UCSD formula.
How this is calculated
Formula: Two ways to convert
chart: about 15 at 1 year, 24 at 2, then 4 to 7 a year by size; UCSD: 16 × ln(dog age) + 31What the symbols mean
- sizeAdult weight: small up to 9 kg, medium 10 to 23 kg, large 23 to 40 kg, giant over 40 kg.
- lnThe natural logarithm.
Good to know
- The UCSD formula comes from DNA changes in Labradors and works for dogs a year and older.
Read the full methodologyFound an error? Contact us
Worked examples
Each example is worked out by the same code as the calculator above.
Large dog, 10 years
About 66 human years.
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<iframe src="/embed/dog-age-calculator" title="Dog age" width="100%" height="720" style="border:0;max-width:42rem" loading="lazy"></iframe>Questions
How old is my dog in human years?
The first year counts as about 15 human years and the second about 9 more. After that small dogs age about 4 a year and large dogs about 5 to 7.
Is one dog year 7 human years?
No, that is an old rule of thumb. Dogs grow up much faster in their first two years and then age more slowly.
Do big dogs age faster?
Yes. After about 5, large and giant breeds age faster and usually have shorter lives than small breeds.
How old is a 5 year old dog in human years?
About 36 for small and medium dogs on the vet chart. The UCSD formula gives about 57.
When is a dog considered a senior?
Around 7 for most dogs and earlier, about 5 or 6, for giant breeds. Vets suggest twice-yearly checks for senior dogs.