What is my dog's age in human years?
The multiply-by-7 rule is outdated. Use the calculator below, based on a 2020 epigenetic study, to find your dog's or cat's real age compared to a human's.
Equivalent human age
49 human years
Life stage: adult.
How the calculation works
For decades, owners used the simple rule of multiplying a dog's age by 7 to estimate their age "in human years." The problem is that this relationship isn't linear: a 1-year-old dog is already physically mature, equivalent to a roughly 31-year-old human — much more than the 7 years the old rule would suggest.
This calculator uses a formula derived from a study published in 2020 in the journal Cell Systems, which compared DNA methylation patterns (an "epigenetic clock") between dogs and humans over their lifespans. The resulting formula is: human age = 16 × ln(dog age) + 31, valid from 1 year of age.
Since larger dogs tend to have shorter life expectancies and age faster in the second half of life, we apply an additional adjustment to the result from age 6 onward: -2 years for small sizes, no adjustment for medium, +3 for large, and +6 for giant.
For puppies under 1 year old, the first-year curve is linearly interpolated in segments (birth, 6 months ≈ 10 human years, 12 months ≈ 31 human years), reflecting the accelerated growth typical of this stage.
Dog age in human years by size
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 year | 31 years | 31 years | 31 years | 31 years |
| 2 years | 42 years | 42 years | 42 years | 42 years |
| 3 years | 49 years | 49 years | 49 years | 49 years |
| 4 years | 53 years | 53 years | 53 years | 53 years |
| 5 years | 57 years | 57 years | 57 years | 57 years |
| 6 years | 58 years | 60 years | 63 years | 66 years |
| 7 years | 60 years | 62 years | 65 years | 68 years |
| 8 years | 62 years | 64 years | 67 years | 70 years |
| 9 years | 64 years | 66 years | 69 years | 72 years |
| 10 years | 66 years | 68 years | 71 years | 74 years |
| 12 years | 69 years | 71 years | 74 years | 77 years |
| 15 years | 72 years | 74 years | 77 years | 80 years |
Cat age in human years
| Cat age | Equivalent human age |
|---|---|
| 1 year | 15 years |
| 2 years | 24 years |
| 3 years | 28 years |
| 4 years | 32 years |
| 5 years | 36 years |
| 6 years | 40 years |
| 7 years | 44 years |
| 8 years | 48 years |
| 9 years | 52 years |
| 10 years | 56 years |
| 12 years | 64 years |
| 15 years | 76 years |
Frequently asked questions
Is the "1 dog year = 7 human years" rule wrong?
Yes, it's a popular myth. The relationship between dog age and human age isn't linear: dogs mature very quickly in their first year of life and slow down afterward. The formula used here is based on a 2020 study that compared epigenetic markers (DNA methylation) between dogs and humans, offering a much more realistic estimate.
Why does the size of the dog affect the equivalent age?
Large and giant dogs have shorter life expectancies and age faster in the second half of life, so we apply an additional adjustment starting at age 6. Small dogs, on the other hand, tend to age more slowly after middle age.
Does the formula work for any breed?
The formula is a general estimate by size, not by specific breed. Breeds with particular genetic predispositions may age somewhat differently from the average of their size group.
Does the cat calculation also use the epigenetic formula?
The cat calculator uses a scale widely accepted by veterinarians (1 year = 15 human years, 2 years = 24, and +4 human years each additional year), since the 2020 epigenetic study focused on dogs.
At what age is a dog considered senior?
In this calculator, we consider "senior" from approximately 56 equivalent human years and "geriatric" from 76 — but the exact timing varies by size and breed; talk to your pet's veterinarian about their specific life expectancy.
Important notice
This calculator is for educational purposes and does not replace a veterinary evaluation. When in doubt, consult a veterinarian.Sources
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