Dog age calculator
Dog years to human years — worked out properly, by size, not by the ×7 rule.
Size when fully grown
10–23 kg · 21–50 lb
A 5-year-old medium dog is about as old as a 39-year-old person. DNA-based estimate: 57.
Three answers to one question
Ask how old a dog is “in human years” and you'll get three different methods. Drag across the chart to see where they agree — and where the ×7 rule goes badly wrong.
The vet chart (red) is what most vets use: about 15 human years for the first year, 9 for the second, then 4 to 7.5 a year depending on size.
The DNA formula (blue) comes from measuring epigenetic ageing in Labradors. It says puppies age extremely fast and old dogs barely at all.
×7 (dashed) undersells puppies and oversells old dogs.
Dog's age in years (drag the chart) → human-equivalent years ↑
- Vet chart (medium dog)39
- DNA-ageing formula57
- The ×7 myth35
Dog years chart
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 3 | 28 | 29 | 30 | 32 |
| 4 | 32 | 34 | 36 | 39 |
| 5 | 36 | 39 | 42 | 47 |
| 6 | 40 | 44 | 48 | 54 |
| 7 | 44 | 49 | 54 | 62 |
| 8 | 48 | 54 | 60 | 69 |
| 9 | 52 | 59 | 66 | 77 |
| 10 | 56 | 64 | 72 | 84 |
| 11 | 60 | 69 | 78 | 92 |
| 12 | 64 | 74 | 84 | 99 |
| 13 | 68 | 79 | 90 | 107 |
| 14 | 72 | 84 | 96 | 114 |
| 15 | 76 | 89 | 102 | 122 |
| 16 | 80 | 94 | 108 | 129 |
Questions
Is one dog year really seven human years?
No. The ×7 rule is a myth from the 1950s. Dogs mature very fast in the first two years — a one-year-old dog is roughly like a 15-year-old human — then age more slowly, at a rate that depends on size.
Why do big dogs age faster?
Large and giant breeds reach adulthood at a similar pace to small dogs but then age faster, which is why a Great Dane is senior at 6 while a Chihuahua may not be until 10 or later.
Which dog-age formula is most accurate?
For everyday use, the size-based vet chart is the most practical. The DNA-based formula (16 × ln(age) + 31) came from a 2020 study of Labrador retrievers and is interesting, but it was not validated across all breeds.
How old is a 1-year-old dog in human years?
About 15 human years — roughly a teenager. By two, a dog is around 24 in human terms regardless of size.
When is my dog considered a senior?
Roughly at 10 for small dogs, 8 for medium, 7 for large and 6 for giant breeds. Vets often suggest twice-yearly check-ups from then on.
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